Ans: $\dfrac{m^9}{n^{10}}$
$\begin{array}{cl}
& \dfrac{(mn^{-2})^5}{m^{-4}} \\
= & \dfrac{m^5n^{-2 \times 5}}{m^{-4}} \\
= & m^{5-(-4)}n^{-10} \\
= & \dfrac{m^9}{n^{10}}
\end{array}$
$\begin{array}{cl}
& \dfrac{(mn^{-2})^5}{m^{-4}} \\
= & \dfrac{m^5n^{-2 \times 5}}{m^{-4}} \\
= & m^{5-(-4)}n^{-10} \\
= & \dfrac{m^9}{n^{10}}
\end{array}$
