Answer:
C. 5 weeks.
Step-by-step explanation:
In this question we have a random variable that is equal to the sum of two normal-distributed random variables.
If we have two random variables X and Y, both normally distributed, the sum will have this properties:

To calculate the expected weeks that the donation exceeds $120, first we can calculate the probability of S>120:

The expected weeks can be calculated as the product of the number of weeks in the year (52) and this probability:

The nearest answer is C. 5 weeks.
Answer (numbers needed in boxes, going from top to bottom):
1
-1
-3
3
Step-by-step explanation:
f(x) is another way of saying y. So, the table is asking, "when substituting these x values for the x's in the function, what does y equal?" So, to answer the question, substitute each x value into the equation and solve.
1) Start with the x value of 1. Substitute 1 for x in y = 2x - 1 and solve:

So, when x equals 1, y equals 1. Therefore, the first box on the top must be filled out with the number 1.
2) Do the same with the rest of the x values. Here are the steps to solve each one, going in order from the top towards the bottom:
x = 0

x = -1
x = 2

Answer:
x=26
Step-by-step explanation:
3x +12 =90
subtract 12 from each side
3x=78
divide 3 from each side
x=26
Answer:
The first step is to replace the y in y-x=15 with 7x (we can do this because the first equation tells us that they're equal)
solve and get
(2.5,17.5)
or x= 2.5 y=17.5
Step-by-step explanation:
The first step is to recognize that y=7x which means that we can just replace the y in the second equation with 7x
7x-x=15
6x=15
x=2.5
Then we can solve for y
y=7(2.5)
y=17.5