The general Formula for a decreasing Annuity is:

For this example we have:
P = 78,000
n = 7*4 = 28
i = 8%/4 = 2% = 0.02
After substituting you can find value for R, rent.
Answer:
27 1/2 cups
Step-by-step explanation:
7 1/2 cups : 3 dozen
7 1/2 /3 = 5/2 tells us we need 5/2 or 2.5 cups for 1 dozen
5/2 x 11 = 27 1/2 cups
Part A
No it’s not a function because the grade can’t have two y-intercept
Part B
Yes it is a function