Ans: $\dfrac{n^5}{m^{12}}$
$\begin{array}{rl}
& \dfrac{m^{-12}n^8}{n^3}\\
= & m^{-12}n^{8-3} \\
= & m^{-12}n^5 \\
= & \dfrac{n^5}{m^{12}}
\end{array}$
$\begin{array}{rl}
& \dfrac{m^{-12}n^8}{n^3}\\
= & m^{-12}n^{8-3} \\
= & m^{-12}n^5 \\
= & \dfrac{n^5}{m^{12}}
\end{array}$
