This is an easy one, but sometimes it becomes tricky for me. Specially when the problem envolves only variables with no numbers.
Mark up can be either an amount or a percentage and usually applies to percent questions.
We usually see mark up as a % change in price of an item. For example:
"If a store buys an item for $15 and then marks it up by 20%, what is the sale price of the item?"
"If after purchasing an item for $n a store marks it up by 25% and then sells the item for $20, what's the value of n?"
