$$\sqrt[4]{\frac{81a^{12}b^{-20}}{16x^{8}y^{-16}}}$$
$\frac{3\left(|a|\right)^{3}y^{4}}{2x^{2}\left(|b|\right)^{5}}$
$-\frac{3\times \left(\frac{|a|}{x}\right)^{3}y^{4}}{\left(|b|\right)^{5}}$
