Please help I'm having difficulty answering this question

Explain how to convert measurements in the metric system

Mrs. robinson bought a novel at a bookstore on sale for 20% off its regular price of $29.99. mr chang bought the same novel at a different bookstore for 10% off its regular price of $25. which person received the better discount?

Given: df and de are midsegments of abc prove: de=1/2 ac