Answer
$h^{-1}(x) = \frac{3x+27}{2}$
Work Step by Step
$h(x) = \frac{2}{3}x -9$
Let $h(x) = y$:
$y = \frac{2}{3}x - 9$
Switch the variables $x$ and $y$ to find the inverse and solve for $y$:
$x = \frac{2}{3}y -9 $
$x + 9 = \frac{2}{3}y$
$x + 9 = \frac{2y}{3}$
$3x + 27 = 2y$
$y = \frac{3x+27}{2}$
$h^{-1}(x) = \frac{3x+27}{2}$