I need these to be simplified.
1) 6-10+1
2) -11+3+20
3) 8+(-15)+(-15)
4) 7-(-1)+18

the answer to your question is c.)   volcanoes built the mountains and earthquakes tore them down.

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).