Your friend has $90 when he goes to the fair. he spends $5 to enter the fair and $15 on food. rides at the fair cost $1.50 per ride. which function can be used to determine how much money he has left over after x rides?

a.) f(x) = 1.5x + 70
b.) f(x) = -1.5x + 70
c.) f(x) = 1.5x - 70
d.) f(x) = -20x + 90