[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{15\% of 20}}{\left( \cfrac{15}{100} \right)20}\implies 3~\hfill \underset{selling~price}{\stackrel{20+3}{23}}[/tex]
