Answer
$\frac{z^{5}}{y^{9}}$
Work Step by Step
We know that $a^{−n}=\frac{1}{a^{n}}$ and $\frac{1}{a^{-n}}=a^{n}$ (as long as a is a nonzero real number and n is an integer).
Therefore, $\frac{y^{-9}}{z^{-5}}=\frac{1}{y^{9}}\times z^{5}=\frac{z^{5}}{y^{9}}$.
