Dan works at a hardware store. The employee discount is determined by the

Question

formula d = 0.15 (c − 10 ). Use the inverse of this function to find the cost of the item for which Dan received an $18.00 discount.
a. Find the inverse function that models cost as a function of the discount.
b. Evaluate the inverse function for d = 18.
c. What was Dan’s final cost for this item?

Answer 1

I don't think you are using the concept of the "inverse of a function" in the proper way, you are just solving the equation for c

d = .15c - 1.5
.15c = d + 1.5
c = (d+1.5)/.15

now plug in d = 18
c = (18+1.5)/.15 = 130

We could have just plugged in d = 18 in the original

18 =.15(c-10)
18/.15 = c-10
120 = c - 10
130 = c