Answer
$$f(\frac{x}{3}) = 2x-18 $$
$$\frac{f(x)}{3} = 2x-6$$
Work Step by Step
For x = $\frac{x}{3}$
$f(\frac{x}{3})= 6(\frac{x}{3}) - 18$ ... multiply and simplify
$=2x -18$
_______________
$f(x) = 6x-18$
therefore
$\frac{f(x)}{3} = \frac{6x-18}{3}$ ... simplify
$=2x -6$
