Answer :
[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{17.1\% of 128}}{\left( \cfrac{17.1}{100} \right)128}\implies 21.888~~ \approx ~~22[/tex]
