Simplify -(xy^-1)/(9z^-2)

$- \frac{x y^{- 1}}{9 z^{- 2}}$

Move $y^{- 1}$ to the denominator using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$- \frac{x}{9 z^{- 2} y}$

Move $z^{- 2}$ to the numerator using the negative exponent rule $\frac{1}{b^{- n}} = b^{n}$ .

$- \frac{x z^{2}}{9 y}$