Martin needed to buy a new bookcase. At the store, he found a bookcase to buy that had a price of $199. However, the bookcase also had a sign which said it was 20% off the original price. How much did Martin pay for the bookcase?
$199 represents 100% of the cost, but since it is 20% off you subtract 20% from the 100%. Then you multiply what you got from the previous step to get your answer.