[tex]\bf \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{25\% of "h"}}{\left( \cfrac{25}{100} \right)h}\implies 0.25h \\\\\\ \stackrel{\textit{Rob spent then}}{\stackrel{\textit{planned hours}}{h}+\stackrel{\textit{extra hours}}{0.25h}}\implies h+0.25h\implies \stackrel{\textit{common factor}}{h(1+0.25)}\implies 1.25h[/tex]
