I’m pretty sure the answer is $80 cents
A. F(x)= 3x+6 =12
3x = 12-6
3x = 6
x=2
B. x=10, f(x)= 3*10+6 = 30+6 = 36
C. f(x) = 3x+6 = 6
3x = 6-6
3x=0
x=0
D. x=5, f(x) = 3x+6 = 3*5+6 = 15+6 = 21
Answer:

And we can solve this using the following z score formula:

And if we use this formula we got:

So we can find this probability equivalently like this:

Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the heights of a population, and for this case we know the distribution for X is given by:
Where
and
We select n =100. Since the distribution for X is normal then we know that the distribution for the sample mean
is given by:
We want this probability:

And we can solve this using the following z score formula:

And if we use this formula we got:

So we can find this probability equivalently like this:

3 is less than 5, so rounded to the nearest ten is 360.
6 is greater than 5, so rounded to the nearest hundred, our answer is 400.
A = account
M = money
w = weeks
A = Mw
Hope this helps! Any questions let me know :)