Answer:
Take each sale price of each product and divide it by its original price. Subtract from 1. Then multiply by 100.

Explanation:
A percent is a portion of 100 or the total. We find the percent we pay by taking each sales price and dividing it by the original price. To find the percent off we take that same number and subtract from 1. This will give a decimal which we can convert to a % by multiplying by 100.