Question

A music store buys compact discs for $12 each and sells them for $15 each. What is the percent of markup?

Answer 1

If we take 12 to be the 100%, now 15 - 12, so is 3 bucks up for the retail price, what is 3 off 12 in percentage then?

$\bf \begin{array}{ccll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 12&100\\ 3&p \end{array}\implies \cfrac{12}{3}=\cfrac{100}{p}\implies p=\cfrac{3\cdot 100}{12}$