Answer
It doesn't make sense.
Work Step by Step
We have to perform the division:
$$\dfrac{3x}{x+2}\div\dfrac{(x+2)^2}{x-4}.$$
In the beginning we transform division into multiplication, so the "common factor" $(x+2)$ is no longer common:
$$\dfrac{3x}{x+2}\div\dfrac{(x+2)^2}{x-4}=\dfrac{3x}{x+2}\cdot\dfrac{x-4}{(x+2)^2}.$$
The factors $(x+2)$ and $(x+2)^2$ are both in the denominator, so we cannot simplify them!
The given statement doesn't make sense.
