Ans: $x^{34}y^{55}$
$\begin{array}{cl}
& \dfrac{x^{-8}y}{(x^7y^9)^{-6}} \\
= & \dfrac{x^{-8}y}{x^{7\times(-6)}y^{9\times(-6)}} \\
= & \dfrac{x^{-8}y}{x^{-42}y^{-54}} \\
= & x^{-8-(-42)}y^{1-(-54)} \\
= & x^{34}y^{55}
\end{array}$
