Solve the following

$\frac{3 x}{5 x+2}=-4$

$\Rightarrow \frac{3 x}{5 x+2}=\frac{-4}{1}$

$\Rightarrow 1(3 x)=-4(5 x+2)$ (by cross multiplication)

$\Rightarrow 3 x=-20 x-8$

$\Rightarrow 3 x+20 x=-8$

$\Rightarrow 23 x=-8$

$\Rightarrow x=\frac{-8}{23}$

$\therefore x=\frac{-8}{23}$