so, 32 - 28 is just 4, thus the difference is 4 minutes then.
if we take 32 to be the 100%, what is 4 off of it in percentage?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
32&100\\
4&p
\end{array}\implies \cfrac{32}{4}=\cfrac{100}{p}\implies p=\cfrac{4\cdot 100}{32}[/tex]
