I think this is the easiest way, but others may disagree
6/(3/4) = (6*4/4)/(3/4) = (24/4)/(3/4) = 24/3 = 8
that is a complicated looking method reinout-g
$$6\div \frac{3}{4}=\frac{6}{1}\times \frac{4}{3}=\frac{2}{1}\times \frac{4}{1}=8$$
You think so?
Here, I put it in LaTeX
$$\frac{6}{\frac{3}{4}} = \frac{6 \times 1}{\frac{3}{4}} = \frac{6 \times \frac{4}{4}}{\frac{3}{4}} = \frac{\frac{6*4}{4}}{\frac{3}{4}} = \frac{\frac{24}{4}}{\frac{3}{4}} = \frac{\frac{24}{ \rlap{/}{4}}}{\frac{3}{\rlap{/}{4}}}= \frac{24}{3} = 8$$
I make both denominators equal so that they can be crossed out.
But your method is pretty simple too. It's what you prefer I guess.