The system of equations has one solution (-1, 1)
Graph of system of linear equationsFrom the question, we are to graph the given system of equations.
The given system of equation is
y + 2x = −1
3y − x = 4
The graph of the given system of equations is shown below.
From the graph, we can observe that the solution to the given system of equation is given by two lines that intersect at the point (-1, 1).
Hence, the system of equations has one solution (-1, 1)
Learn more on Graph of linear equations here: https://brainly.com/question/14323743
#SPJ1
I think the answer is A. The first one
The data to the right represent the cost of living for 20 states. The cost of living is a measure of the average price paid for housing, utilities, groceries, healthcare, transportation, and miscellaneous expenses. The national average cost of living is 100. The data can be used to compare a state to the national average and to other states.
The frequency distribution based on the information given is illustrated below.
What is the frequency distribution of table?A frequency distribution table is the
chart that summarizes all the data under two columns - variables/categories, and their frequency.
It should be noted that the distribution table has two or three columns and the first column lists all the outcomes as individual values or in the form of class intervals, depending upon the size of the data set.
Given the above information the frequency distribution table is:
Cost of living Number of states
85.0 - 94.9 9
95.0 - 104.9 5
105.0 - 114.9 0
115.0 - 124.9 2
125.0 - 134.9 2
135.0 - 144.9 1
145.0 - 154.9 1
Learn more about frequency distribution on:
https://brainly.com/question/1094036
#SPJ1
7
O x-3
O x-1
O x + 1
O x + 3
3
2-
What must be a factor of the polynomial function f(x) graphed on the coordinate plane below?
3
N
3
I NEED HELP !!!!!
Answer:
x-1 gave ggs is it correct
a fisherman travels 9mi downstream with the current in the same time he travels 3 mi upstream against the current. if the speed of the current is 5mph what is the speed at which the fisherman travels in still water
Answer:
10 mph
Step-by-step explanation:
speed of boat in still water = x
speed of current = 5
speed of boat with current (downstream) = x + 5
speed of boat against current (upstream) = x - 5
distance downstream = 9
distance upstream = 3
time = t
speed = distance/time
distance = speed × time
downstream:
9 = (x + 5)t
upstream:
3 = (x - 5)t
9 = xt + 5t
3 = xt - 5t
9 = xt + 5t
-3 = -xt + 5t
-----------------
6 = 10t
t = 0.6
9 = (x + 5)0.6
15 = x + 5
x = 10
what the milk and and butter
Answer:
1/4 cups of milk and 1 1/3 Tbsp of butter.
Step-by-step explanation:
Milk : 3/4 multiplied by 1/3 = 3/12 = 1/4
Butter : 4 multiplied by 1/3 = 4/3 = 1 1/3
What are the first five terms in the recursive sequence defined by the following? (only one is correct)
a1= 1
a2=1
an= an-2+an-1
a) {1,1,2,3,5}
b) {1,1,0,-1,-1}
c) {2,3,5,8,13}
d) {1,-1,2,-3,5}
Answer:
d 1-12-3-5 is the answer
Carey's annual salary is $67 600 before tax.
How much is his weekly salary before tax?
[Assume 52 weeks in a year.]
Carey's weekly salary before tax is $1300.
What is the weekly salary before tax?The mathematical operation that would be used to determine the required value is division. Division is a mathematical operation that entails grouping a number into equal parts using another number.
In order to determine Carey's weekly salary before tax, divide the yearly salary by the number of weeks in a year.
Carey's weekly salary before tax = yearly salary / number of weeks in a year
$67,600 / 52 = $1300
To learn more about division, please check: https://brainly.com/question/13281206
#SPJ1
PLSSSSSSSS HELPPPPPP AYUDAAAAAAS
Answer:
(3+3) x (3+1)
Step-by-step explanation:
» (1 + 3) × (3 + 3)
» (4) × (6)
» 24
Here's our answer..!!
01
5. Solve the polynomial by typing it into a graphing calculator and identifying the zeros. Round to the nearest tenth.
5x^4-7x^3-5x^2+5x+1=0
Answer:
-0.8, -0.2, 0.8, 1.6
Step-by-step explanation:
If 5 bags weigh the same as 3 blocks, how many blocks will 9 bags weigh?
OA) 3 blocks
OB) 4.4 blocks
OC) 5.4 blocks
OD) 15 blocks
Answer: C. 5.4 Blocks
Step-by-step explanation:
Given information
5 bags = 3 blocks
Set variable
Let x be the number of blocks
Constructure proportional equation
[tex]\frac{3}{5} } ~=~\frac{x}{9}[/tex]
Cross multiply the fraction
[tex](3)~*~(9)~=~(5)~*~(x)[/tex]
[tex]27~=~5x[/tex]
Divide 5 on both sides
[tex]27~/~5~=~5x~/~5[/tex]
[tex]\Large\boxed{x=5.4~blocks}[/tex]
Hope this helps!! :)
Please let me know if you have any questions
Answer:
oc
Step-by-step explanation:
5 times .6 equals 3
9 times .6 equals 5.4
In pentagon ABCDE shown above, each side is 1 cm. If a particle starts at point A and travels clockwise 723 cm along ABCDE, at which point will the particle stop?
The particle will stop at D.
What is the fundamental principle of multiplication?If an event can occur in m different ways and if following it, a second event can occur in n different ways, then the two events in succession can occur in m × n different ways.
In pentagon ABCDE shown above, each side is 1 cm. If a particle starts at point A and travels clockwise 723 cm along ABCDE, then
Number of sides = 5
Let x be the one complete revolution.
5 x = 725
x = 145
Now, 145 - 2 = 143
Hence, it will stop at D which is 2 less than A.
Learn more about multiplications;
https://brainly.com/question/14059007
#SPJ1
Captain's Autos sells 22 used cars on
Monday, and 18 cars on Tuesday. This was
25% of the number of sales for the week.
How many cars did they sell altogether that
week
Answer:
160
Step-by-step explanation:
22 + 18 = 25 percent
40 = 25 percent
100 / 25 = 4
40 x 4 = 160.
pLEASE answer as fast as possible REALLY URGENT
Using proportions, it is found that you would expected the white counter to be chosen 128 times.
What is a proportion?A proportion is a fraction of a total amount, and the measures are related using a rule of three. Due to this, relations between variables, either direct or inverse proportional, can be built to find the desired measures in the problem.
From the table, the proportion of the white counter is given as follows:
p = 32/(32 + 18) = 32/50 = 0.64.
Hence, out of 200 trials, the number of trials in which the white counter is expected to be chosen is given by:
0.64 x 200 = 128 times.
More can be learned about proportions at https://brainly.com/question/24372153
#SPJ1
At a hockey game, a vender sold a combined total of 210 sodas and hot dogs. The number of sodas sold was 36 more than the number of hot dogs sold. Find the number of sodas sold and the number of hot dogs sold.
Answer:
123 soda and 87 hot dogs
Step-by-step explanation:
Let s = # soda and h = # hot dogs
s + h = 210 s = h + 36 Substitute the h + 36 for s into the first equation
s + h = 210
(h + 36) + h = 210
h + 36 + h = 210 Combine the h's
2h + 36 = 210 Subtract 36 from both sides
2h = 174 Divide both sides by 2
h = 87 This is the number of hot dogs. Substitute this into either equation above to find the sodas.
s + h = 210
s + 87 = 210
s = 123
OR
s = h + 36
s = 87 + 36
s = 123
Question 8
Ben decides to build a rabbit run to keep his children's rabbits in. The run will be
rectangular with a width of 4 m. He has a maximum of 34 m of fencing to use, but
wants the area to be greater than 50 m². Find the range of values for the length of
the run, using inequalities.
Riverbed company purchased a delivery truck for $33,000 on January 1, 2022 the truck has an expected salvage value of 2760 and he suspected to be driven 108,000 miles over estimated useful life of 10 years actual miles driven was 16,000 802,022 and 12,000 602,023 how much is the depreciation expense per mile
Answer:
0.28
Step-by-step explanation:
Depreciation Expense per mile:
= (Cost of delivery truck - Salvage value) ÷ Expected miles driver
=(33000-2760)÷108000=0.28 per mile
A radar unit is used to measure speeds of cars on a miter way the speed are normally distributed with a mean of 90 km/hr and a standard deviation of 10 km/hr what is the probability that’s a car picked at random is traveling at more than 100 km/hr
Using the normal distribution, there is a 0.1587 = 15.87% probability that’s a car picked at random is traveling at more than 100 km/hr.
Normal Probability DistributionThe z-score of a measure X of a normally distributed variable with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex] is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
The z-score measures how many standard deviations the measure is above or below the mean. Looking at the z-score table, the p-value associated with this z-score is found, which is the percentile of X.The mean and the standard deviation are given, respectively, by:
[tex]\mu = 90, \sigma = 10[/tex]
The probability that’s a car picked at random is traveling at more than 100 km/hr is one subtracted by the p-value of Z when X = 100, hence:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]Z = \frac{100 - 90}{10}[/tex]
Z = 1
Z = 1 has a p-value of 0.8413.
1 - 0.8413 = 0.1587.
0.1587 = 15.87% probability that’s a car picked at random is traveling at more than 100 km/hr.
More can be learned about the normal distribution at https://brainly.com/question/28096232
#SPJ1
Geometry and Modeling:
Mike completely filled the container shown below with 616 small cubes that were each [tex]\frac{1}{2}[/tex] inch long.
Part A: Calculate the volume of the prism.
Part B: Crate a graphical model of a prism with base 5.5 by 3.5 that has the same volume as Part A.
Show how Mike can calculate the volume of the prism, in cubic inches, by using a volume formula instead of filling the container with small cubes.
ASAP HELP ME WITH THIS QUESTION
Which expression represents the
number of reams of paper the company
produced during the second year?
The expression that represents the number of reams of paper the company produced during the second year is 4.704 × 10¹⁰. The correct option is D. 4.704 × 10¹⁰
Writing an ExpressionFrom the question, we are to determine the expression that represents the number of reams of paper the company produced during the second year
From the given information,
During the first year of operation,
The company produced 8.4 × 10⁹ reams of paper
And
During the second year,
the company produced 5.6 times the number of reams of paper that it produced during the first year.
Thus,
The number of reams of paper the company produced during the second year = 5.6 × 8.4 × 10⁹ reams of paper
The number of reams of paper the company produced during the second year = 47.04 × 10⁹ reams of paper
= 4.704 × 10¹ × 10⁹ reams of paper
= 4.704 × 10¹⁰ reams of paper
Hence, the expression that represents the number of reams of paper the company produced during the second year is 4.704 × 10¹⁰. The correct option is D. 4.704 × 10¹⁰
Learn more on Writing an expression here: https://brainly.com/question/20885119
#SPJ1
after henry gave away 2/3 of his stamps and ken gave away 3/4 of his the two boys had an equal number of the stamps left. they had 1156 stamps at first how many stamps did they have left altogather
Answer:
See below.
If the correct sum is 1155, then Ken had 495 stamps, and Henry had 660 stamps.
Step-by-step explanation:
Henry had h stamps.
Ken had k stamps.
After giving away 2/3 of his stamps, Henry ended up with 1/3 of his stamps, or h/3.
After giving away 3/4 of his stamps, ken ended up with 1/4 of his stamps, or k/4.
h/3 = k/4
h + k = 1156
4h = 3k
h = 1156 - k
4(1156 - k) = 3k
4624 - 4k = 3k
4624 = 7k
k = 4624/7
Stamps left: 0.25 × 4624/7 = 1156/7
h = 1156 - k
h = 1156 - 4624/7
h = 8092/7 - 4624/7
h = 3468/7 =495.43
Stamps left: 1/3 × 3468/7 = 1156/7
Total number of stamps left: 1156/7 + 1156/7 = 2312/7 = 330.29
The problem is solved correctly, but the numbers given must be incorrect since you cannot have a fraction of a stamp.
hey can you help me answer this question by giving me the answer?
The value of f(a)=4-2a+6[tex]a^{2}[/tex], f(a+h) is [tex]6a^{2} +6h^{2} -2a-2h+12ah[/tex] , [f(a+h)-f(a)]/h is 6h+12a-2 in the function f(x)=4-2x+6[tex]x^{2}[/tex].
Given a function f(x)=4-2x+6[tex]x^{2}[/tex].
We are told to find out the value of f(a), f(a+h) and [f(a+h)-f(a)]/hwhere h≠0.
Function is like a relationship between two or more variables expressed in equal to form.The value which we entered in the function is known as domain and the value which we get after entering the values is known as codomain or range.
f(a)=4-2a+6[tex]a^{2}[/tex] (By just putting x=a).
f(a+h)==[tex]4-2(a+h)+6(a+h)^{2}[/tex]
=4-2a-2h+6([tex]a^{2} +h^{2} +2ah[/tex])
=4-2a-2h+6[tex]a^{2} +6h^{2} +12ah[/tex]
=[tex]6a^{2} +6h^{2}-2a-2h+12ah[/tex]
[f(a+h)-f(a)]/h=[[tex]6a^{2} +6h^{2}-2a-2h+12ah[/tex]-(4-2a+6[tex]a^{2}[/tex] )]/h
=[tex](6a^{2} +6h^{2} -2a-2h+12ah)/h[/tex]
=[tex](6h^{2} -2h+12ah)/h[/tex]
=6h+12a-2.
Hence the value of function f(a)=4-2a+6[tex]a^{2}[/tex], f(a+h) is [tex]6a^{2} +6h^{2} -2a-2h+12ah[/tex] , [f(a+h)-f(a)]/h is 6h+12a-2 in the function f(x)=4-2x+6[tex]x^{2}[/tex].
Learn more about function at https://brainly.com/question/10439235
#SPJ1
what is 4,928 will rounded to the nearest hundred
Answer:
4900
Step-by-step explanation:
When rounding a number such as 4928 to the nearest hundred, we use the following rules:
A) We round the number up to the nearest hundred if the last two digits in the number are 50 or above.
B) We round the number down to the nearest hundred if the last two digits in the number are 49 or below.
C) If the last two digits are 00, then we do not have to do any rounding, because it is already to the hundred.
In this case, Rule B applies and 4928 rounded to the nearest hundred is:
4900
Answer:
Step-by-step explanation:
4,928, look at the last two numbers 28 if they are above 50 you round up, if below 50 round down,
The answer is 4,900
Two cyclists start at the same point and travel in opposite directions. One cyclist travels 5 faster than the other. If the two cyclists are 74 miles apart after 2 hours, what is the rate of each cyclist?
The rate of the slower cyclist is 16 mph while the rate of the faster cyclist is 21 mph.
How to calculate the rate of speed?let us assume the following;
x = rate of slower cyclist
x + 5 = rate of faster cyclist
We know that formula for distance is;
distance = travel time*rate
Thus;
2x + 2(x + 5) = 74
Since the two cyclists are a distance of 74 miles apart after a time 2 hours. Thus;
2x + 2x + 10 = 74
4x + 10 = 74
4x = 74 - 10
4x = 64
x = 64/4
x = 16
Rate of faster cyclist = 16 + 5 = 21 mph
Read more about Rate of Speed at; https://brainly.com/question/2681210
#SPJ1
change the following fraction to a percent 4/50
Answer:
For finding Percentage u have to multiply the number with 100
e.g.,
[tex] \frac{4}{50} \times 100[/tex]
[tex]4 \times 2 = 8\%[/tex]
Hopefully this helps u...
Please mark me as brainlist
A machine is programmed to run an algorithm for 972 hours starting at 9 A.M. on Monday. When will the machine stop running the algorithm.
A) 9 A.M. on Saturday
B) 9 P.M. on Saturday
C) 9 A.M. on Sunday
D) 9 P.M. on Sunday
Using proportions, it is found that the correct option for when the machine will stop running the algorithm is:
B) 9 P.M. on Saturday.
What is a proportion?A proportion is a fraction of a total amount, and the measures are related using a rule of three. Due to this, relations between variables, either direct or inverse proportional, can be built to find the desired measures in the problem.
The algorithm runs for 972 hours. Each day has 24 hours, hence we apply the proportion to find the number of days as follows:
972/24 = 40.5 days.
The remainder of the division of 40.5 by 7, as a week has 7 days, is of 5.5, which means that the code will finish running 5.5 days after the 9 A. M. Monday, that is at 9 P. M. on a Saturday, which means that option B is correct.
More can be learned about proportions at https://brainly.com/question/24372153
#SPJ1
In 2016, the CDC estimated the mean weight of U.S. women over the age of 20 years old was 168.5 pounds with a standard deviation of 68 pounds.
1. What is the expected mean for a sample of 150 women?
2. What is the standard deviation of the mean for a sample of 150 women?
3. What is the probability of 150 women having a sample mean below 160 pounds?
4. What is the probability of 150 women having a sample mean above 175 pounds?
5. What is the probability of 200 women having a sample mean below 160 pounds? Note the change in sample size.
6. What is the probability of 200 women having a sample mean above 175 pounds?
Step-by-step explanation:
1.
the expected sample mean is always the general mean : 168.5 pounds.
2.
the SD of a sample is the general SD / sqrt(sample size).
in our case
the sample SD = 68/sqrt(150) = 5.55217675...
3.
if we are looking for only the probability that any single woman is below 160 pounds, we would use the normal z calculation :
z = (x - mean)/SD = (160 - 168.5)/68 = -8.5/68
but we have here the question about the probability of the mean value of a whole sample of 150 women.
so, we need to adapt the z-calculation by the principle of 2) for the SD of a sample :
z = (x - mean)/(SD × sqrt(sample size)) =
= (160 - 168.5)/(68 × sqrt(150)) = -8.5/(68×sqrt(150)) =
= -0.010206207 ≈ -0.01
that gives us in the z-table the p-value 0.49601
this 0.49601 is the probability that a sample of 150 women has a mean value of below 160 pounds.
4.
similar to 3.
the z value we are looking for
z = (175 - 168.5)/(68 × sqrt(150)) = 6.5/(68 × sqrt(150)) =
= 0.007804747... ≈ 0.01
that gives us the p-value 0.50399.
that would be the probability of a sample mean of 175 or below.
to get above 175 we need to get the other side of the bell-curve :
1 - 0.50399 = 0.49601
so, this case has about the same probability as 3.
5.
as 3), just with the sqrt(200) instead of the sqrt(150).
z = -8.5/(68 × sqrt(200)) = -0.008838835... ≈ 0.01
so, the probability is still about the same as in 3) :
0.49601
6.
as 4) just with sqrt(200).
z = 6.5/(68 × sqrt(200)) = 0.006759109... ≈ 0.01
so, the probability is still about the same as for 4) :
0.49601
The answers are :
1) The expected mean for a sample of 150 women is 168.5 pounds.
2) The standard deviation (SD) of the mean for a sample of 150 women is 5.55.
3) The probability of 150 women having a sample mean below 160 pounds will be 0.49601.
4) The probability of 150 women having a sample mean above 175 pounds will be 0.49601.
5) The probability of 200 women having a sample mean below 160 pounds will be 0.49601.
6) The probability of 200 women having a sample mean above 175 pounds will be 0.49601.
What is probability ?
Probability is a measure of the likelihood of event to occur. The probability of all the events in a sample space adds up to 1.
1)
We know that the expected mean of a sample is always equal to general mean.
As per the question, mean weight is 168.5 pounds.
This implies :
The expected mean for a sample of 150 women is :
= 168.5 pounds
2)
The standard deviation (SD) of the mean for a sample of 150 women is :
= 68 / (√150)
= 5.55
3)
The probability of 150 women having a sample mean below 160 pounds will be represented by z and will be :
z = ( x - mean) / ( SD × (√sample size))
= (160 - 168.5) / (68 × √150)
= 0.01
If we use the z table then the probability will be :
= 0.49601
4)
Similarly as part 3 :
z = (175 - 168.5) / (68 × √150)
z = 0.01 (approximately)
The probability of 150 women having a sample mean below 175 pounds will be :
= 0.50399
And the probability of 150 women having a sample mean above 175 pounds will be :
= 1 - 0.50399
= 0.49601
5)
Here , we have to find probability of 200 women , so 150 in formula of z in 3rd part will be replaced by 200.
i.e.,
z = (160 - 168.5) / (68 × √200)
z = 0.01 ( approximately)
and probability will be :
= 0.49601
6)
Here , we have to find probability of 200 women , so 150 in formula of z in 4th part will be replaced by 200.
z = (175 - 168.5) / (68 × √200)
z = 0.01
And probability equal to :
= 0.49601
Therefore , the answers are :
1) The expected mean for a sample of 150 women is 168.5 pounds.
2) The standard deviation (SD) of the mean for a sample of 150 women is 5.55.
3) The probability of 150 women having a sample mean below 160 pounds will be 0.49601.
4) The probability of 150 women having a sample mean above 175 pounds will be 0.49601.
5) The probability of 200 women having a sample mean below 160 pounds will be 0.49601.
6) The probability of 200 women having a sample mean above 175 pounds will be 0.49601.
Learn more above probability here :
https://brainly.com/question/1846009
#SPJ2
Marin corporation had a projected benefit obligation of $3235000 and plan assets of $3474000 at January 1, 2020 . Marin also had a net acturial loss of $505740 in accumulated OCI at January 1, 2020.The average remaining service period of Marin's employees is 7.80 years . Compute Marin's minimum amortization of the actuarial loss. Minimum amortization of the actuarial loss
the minimum amortization is given as 20300 dollars
How to solve for the amortizationWe have the value of A to be $3235000
while we have the value of B to be $3474000
Of these two values the greatest or the highest is that of the option B.
Next we have to find the corridor value using 10 percent
0.10 * 3474000
= 347400
$505740 - 347400
= 158340
The number of years = 7.8
minimum amortization = 158340/7.8
= 20300 dollars
Hence the minimum amortization is given as 20300 dollars
Read more on amortization here:
https://brainly.com/question/10561878
#SPJ1
need heeeelp please
Answer:
x = 1.086
Step-by-step explanation:
Formula
6^x = 7 Take the log of both sides.
Solution
log 6^x = log 7 Bring the power down You are now dealing with log 6
x * log 6 = log 7 Divide by log 6
x = log 7/log 6
x = .8451 / .7782 Divide
Answer
x = 1.086
In 1965, about 44% of the U.S. adult population had never smoked cigarettes. A national health survey of 1360 U.S. adults (selected randomly) during 2020 revealed that 626 had never smoked cigarettes. Using α = 0.05, test whether there has been a change since 1965 in the proportion of U.S. adults that have never smoked cigarettes. State the hypotheses, list and check the conditions, calculate the test statistic, find the p-value, and make a conclusion in a complete sentence related to the scenario.
Using the z-distribution, it is found that since the p-value is greater than 0.05, there is not enough evidence to conclude that there has been a change since 1965 in the proportion of U.S. adults that have never smoked cigarettes.
What are the hypothesis tested?At the null hypothesis, it is tested if the proportion is still of 44%, that is:
[tex]H_0: p = 0.44[/tex]
At the alternative hypothesis, it is tested if the proportion is now different of 44%, that is:
[tex]H_1: p \neq 0.44[/tex]
What is the test statistic?The test statistic is given by:
[tex]z = \frac{\overline{p} - p}{\sqrt{\frac{p(1-p)}{n}}}[/tex]
In which:
[tex]\overline{p}[/tex] is the sample proportion.p is the proportion tested at the null hypothesis.n is the sample size.For this problem, the parameters are:
[tex]p = 0.44, n = 1360, \overline{p} = \frac{626}{1360} = 0.4603[/tex]
Hence the test statistic is:
[tex]z = \frac{\overline{p} - p}{\sqrt{\frac{p(1-p)}{n}}}[/tex]
[tex]z = \frac{0.4603 - 0.44}{\sqrt{\frac{0.44(0.56)}{1360}}}[/tex]
z = 1.51
What is the p-value and the conclusion?Using a z-distribution calculator, for a two-tailed test, as we are testing if the proportion is different of a value, with z = 1.51, the p-value is of 0.1310.
Since the p-value is greater than 0.05, there is not enough evidence to conclude that there has been a change since 1965 in the proportion of U.S. adults that have never smoked cigarettes.
More can be learned about the z-distribution at https://brainly.com/question/16313918
#SPJ1
The average THC content of marijuana sold on the street is 10.5%. Suppose the THC content is normally distributed with standard deviation of 2%. Let X be the THC content for a randomly selected bag of marijuana that is sold on the street. Round all answers to 4 decimal places where possible,
a. What is the distribution of X? X ~ N(
,
)
b. Find the probability that a randomly selected bag of marijuana sold on the street will have a THC content greater than 8.9.
c. Find the 76th percentile for this distribution.
%
a. This information is given to you.
b. We want to find
[tex]\mathrm{Pr}\{X > 8.9\}[/tex]
so we first transform [tex]X[/tex] to the standard normal random variable [tex]Z[/tex] with mean 0 and s.d. 1 using
[tex]X = \mu + \sigma Z[/tex]
where [tex]\mu,\sigma[/tex] are the mean/s.d. of [tex]X[/tex]. Now,
[tex]\mathrm{Pr}\left\{\dfrac{X - 10.5}2 > \dfrac{8.9 - 10.5}2\right\} = \mathrm{Pr}\{Z > -0.8\} \\\\~~~~~~~~= 1 - \mathrm{Pr}\{Z\le-0.8\} \\\\ ~~~~~~~~ = 1 - \Phi(-0.8) \approx \boxed{0.7881}[/tex]
where [tex]\Phi(z)[/tex] is the CDF for [tex]Z[/tex].
c. The 76th percentile is the value of [tex]X=x_{76}[/tex] such that
[tex]\mathrm{Pr}\{X \le x_{76}\} = 0.76[/tex]
Transform [tex]X[/tex] to [tex]Z[/tex] and apply the inverse CDF of [tex]Z[/tex].
[tex]\mathrm{Pr}\left\{Z \le \dfrac{x_{76} - 10.5}2\right\} = 0.76[/tex]
[tex]\dfrac{x_{76} - 10.5}2 = \Phi^{-1}(0.76)[/tex]
[tex]\dfrac{x_{76} - 10.5}2 \approx 0.7063[/tex]
[tex]x_{76} - 10.5 \approx 1.4126[/tex]
[tex]x_{76} \approx \boxed{11.9126}[/tex]