So Big G gets a great deal on a sofa...$172.80...the original price has to be higher, right? He (? She?) got 36% off...This means that they DID NOT pay 36%, but they DID pay 64% (bc 36 + 64 = 100%)
SO, you need to change percents to decimals to work with them in an equation. Let p be the original price. Original price times 64% will equal the sale price.