Which difference is about 10?
a. 33.2-28.4
b. 70.9-58.7
c. 42.5-16.8
d. 65.7-65.6

D. 65.7-65.6

(the exact difference is 10.1, which is "about" 10)

17 1/3

step-by-step explanation:

the revenue of the fitness center, y, is the product of two factors: the number of members and the fee paid by each member. there are 320 members now, but number of members goes down by 10 for each $5 increase in fees, so if x is the number of $5 price increases then members is equal to (320 - 10x). since the fee is currently $45, and the fee increases by $5 for every price bump x, the fee is given by (45 + 5x). so, revenue y is given by y = (320 - 10x)(45 + 5x).