well, 63 - 36 is 27.
so, if we take 36 to be the 100%, what is 27 in percentage off of it?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
36&100\\
27&p
\end{array}\implies \cfrac{36}{27}=\cfrac{100}{p}\implies p=\cfrac{27\cdot 100}{36}[/tex]
