Solve the following

$\frac{7 y}{5}=y-4$

By cross multiplication:

$\Rightarrow 7 y=5(y-4)$

$\Rightarrow 7 y=5 y-20$

$\Rightarrow 7 y-5 y=-20$

$\Rightarrow 2 y=-20$

$\Rightarrow y=\frac{-20}{2}=-10$

$\therefore y=-10$