to get the inverse of any expression, we first do a quick switcharoo on the variables, then solve for "y", so let's do so,
[tex]\bf y=x+\cfrac{3}{4}\qquad inverse\implies \boxed{x}=\boxed{y}+\cfrac{3}{4}
\\\\\\
x-\cfrac{3}{4}=\stackrel{\stackrel{f^{-1}(x)}{g(x)}}{y}[/tex]