the trick being, you flip the ratio as needed, hmmm in this case we want 750 oz converted to lbs, so hmmm we'd want to cancel out the "oz" part and only leave the "lbs" part,
[tex]750~~~\begin{matrix} oz \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}~~\cfrac{1lbs}{16~~\begin{matrix} oz \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}~~}\implies \cfrac{750}{16}lbs\implies 46.875lbs[/tex]
notice, to cancel out the "oz", we placed the 16 at the bottom.
