1/3 of 3/4 is simply their product.
[tex]\bf \stackrel{\textit{one third of three quarters}}{\cfrac{1}{~~\begin{matrix} 3 \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}~~}\cdot \cfrac{~~\begin{matrix} 3 \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}~~}{4}\implies \cfrac{1}{4}}[/tex]
