[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{20\% of 1500}}{\left( \cfrac{20}{100} \right)1500}\implies 300~\hfill \stackrel{\textit{cost of the book on sale}}{1500-300\implies 1200}[/tex]
