Answer:
36.76
Explanation:
You are taking the original cost and subtracting 15% from it.
x - 15%x = 31.25
x - 15% = x - 15/100 = (100x - 15x)/100
85x/100 = 31.25 Multiply by 100
85x = 31.25 * 100
85x = 3125 Divide by 85
x = 3125 / 85
x = 36.76
When you check to see if this works, you are out about 1/2 a cent. That comes about because there was a slight error in rounding. The computer will still mark your answer (36.76) as correct.