Answer:
I think you might be able to work with this: 0.15 * x - x + x * 0.06
Step-by-step explanation:
The item's cost is X.
So he has a coupon for 15%, so the cost of the item times 0.15 = how much he's getting as a discount, for example: A toy robot costs 13.46, Jenny has a coupon for 25% off, to find out how much she paid, multiply 0.25 by 13.46 which equals about 3.37, so 13.46 - 3.37 = 10.09
So 0.15 (the coupon price) * x (the item's original price) - x (the items orignal price) + x * 0.06 (the sales tax)
Comment if you need any help T^T