so the price is 10.99, up with the tax goes to 11.53, so the tax amount is really 11.53 - 10.99, or $0.54, 54 cents.
now, if we take 10.99 to be the 100%, what is 0.54 in percentage off of it?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
10.99&100\\
0.54&t
\end{array}\implies \cfrac{10.99}{0.54}=\cfrac{100}{t}\implies t=\cfrac{0.54\cdot 100}{10.99}[/tex]
