so, 9.66 - 9.53 will then be 0.13, so if we take 9.66 to be the 100%, what is 0.13 off of it in percentage then?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
9.66&100\\
0.13&p
\end{array}\implies \cfrac{9.66}{0.13}=\cfrac{100}{p}\implies p=\cfrac{0.13\cdot 100}{9.66}[/tex]