[tex]\begin{array}{|c|ll} \cline{1-1} \textit{a\% of b}\\ \cline{1-1} \\ \left( \cfrac{a}{100} \right)\cdot b \\\\ \cline{1-1} \end{array}~\hspace{5em}\stackrel{\textit{10\% of 11}}{\left( \cfrac{10}{100} \right)11}\implies 1.1~\hfill \stackrel{\textit{11 bucks plus tax}}{11+1.1\implies 12.1}[/tex]