Answer
$$ x=-60. $$
Work Step by Step
Since $3$ and $5$ are factors of $15$, we multiply both sides by $15$ and then combine the like terms to get:
$$\frac{x}{3}-4=\frac{2x}{5}\Longrightarrow 15(\frac{x}{3}-4)=\frac{2x}{5}\cdot 15\Longrightarrow 5x-60=6x\\ \Longrightarrow x=-60. $$
