You multiply 125 by 0.80. This is because 125 is the original amount nd to find out how much you have to pay, you would subtract 20% from 100% to get 80%. Now, you know that you have to pay for 80% of the stereo. In order to multiply the two numbers together, you have to convert 80% to a decimal which is 0.80. Lastly, you multiply to get 1oo. Therefore, the stereo costs $100.00 during the sale.
