To easily figure the new cost when there is a percentage off, find out the store's marked price. Say a shower curtain is marked at $60. If you're at a store that is going out of business and they are offering 70 percent off everything in the store, determine what percentage you will have to pay. That number is 30 percent. (70 percent + 30 percent = 100 percent)
Now that you know that you will have to pay 30 percent of the original price, multiply the marked price by the percentage you will have to pay. In this case, it is $60 x 30 percent, which equals $18.
This simplified way to easily figure the new cost when there is a percentage off eliminates subtracting and all the cumbersome math work that isn't really needed.