Answer
$g^{-1}(x) = \log_5 \frac{x}{6}$
Work Step by Step
$g(x) = 6(5^{x})$
Let $g(x) = y$
$y = 6(5^{x})$
Swap the $x$ and $y$ variable to find the inverse:
$x = 6(5^{y})$
$\frac{x}{6} = 5^{y}$
$y = \log_5 \frac{x}{6}$
$g^{-1}(x) = \log_5 \frac{x}{6}$