Question

The marching band of a school is holding a fundraiser. They are charging seven dollars to wash a car and they spent 45 dollars to rent space at a local business that will provide the water they need. The club also spent 60 dollars on soap and other supplies. Choose the function that best models their fundraiser based on the information given.
a) F(x)=45x+60

b) F(x)=60x+45

c) F(x)=7x+105

d) F(x)=7x−105

Answer 1

D. F(x) = 7x − 105 because however many cars they wash and the amount of money they gain from it, they will still have a combined $105 to spend on the supplies and space.

Answer 2

We recognize the fixed costs as 

1. The cost to rent space = $45
2. The cost for soap and other supplies = $60

Our variable in this equation is the number of cars washed, x. Thus, the fundraiser total amount, f(x), is

f(x) = 7x - 105

This is because we are earning $7 per car wash, but we must subtract off the cost of running the fundraiser which is the sum of 1 and 2 above.