Your question is ambiguous, but first let me put what I think your expression is: ⅔x-4.
Inverse can mean reciprocal, so let’s see what the reciprocal would be. ⅔x-4=(2x-12)/3.
This makes the reciprocal 3/(2x-12).
Inverse can also mean inverse function, so if y=⅔x-4, y+4=⅔x, 3(y+4)=2x, x=3(y+4)/2. So if y=f(x)=⅔x-4, then f(y)=3(y+4)/2 and the inverse function is g(x)=f⁻¹(x)=3(x+4)/2.