so it cost them 89.97 and they're selling it for 139.99, the difference is 50.02.
so, the markup is 50.02, if we take 89.97 to be the 100%, how much is 50.02 off of that in percentage?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
89.97&100\\
50.02&p
\end{array}\implies\cfrac{89.97}{50.02}=\cfrac{100}{p}\implies p=\cfrac{50.02\cdot 100}{89.97}[/tex]
