Ans: $\dfrac{y^7}{x^{10}}$
$\begin{array}{cl}
& \dfrac{x^{20}y^{13}}{(x^5y)^6} \\
= & \dfrac{x^{20}y^{13}}{x^{30}y^6} \\
= & \dfrac{y^7}{x^{10}}
\end{array}$
$\begin{array}{cl}
& \dfrac{x^{20}y^{13}}{(x^5y)^6} \\
= & \dfrac{x^{20}y^{13}}{x^{30}y^6} \\
= & \dfrac{y^7}{x^{10}}
\end{array}$
