Answer
$f^{-1}(x)=2x+3$
Work Step by Step
Replace $f(x)$ by $y$ to have:
$y=\dfrac{x-3}{2}$
Interchange $x$ and $y$ then solve for $y$ to have:
$x = \dfrac{y-3}{2}
\\2x= y-3
\\2x+3=y
\\y=2x+3$
Replace $y$ with $f^{-1}(x)$ to have:
$f^{-1}(x)=2x+3$
