it was 150, went down to 100, so it went 50 bucks.
now, if we take 150 as the 100%, what is 50 off of it in percentage?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
150&100\\
50&p
\end{array}\implies \cfrac{150}{50}=\cfrac{100}{p}\implies p=\cfrac{50\cdot 100}{150}[/tex]
