A store owner uses a selling price of 125%of the cost of an item. If a pair of jeans has a sales price of 33.50, what cost does the store owner pay for the pair of jeans?

Which number produces a rationale number when multiplied by 1/5

Having a hard time understanding this question (see attachment).

Agroup of three friends order a combo meal which includes two slices of pizza and a drink each drink is priced at $2.50 the combined total of $31.50 how much is the cost of a slice of pizza