Question

Given f(x)=x+5 all over 3, solve for f^-1(3)

Answer 1

Think of f(x) as y(x) and inverse function as x(y).
$f^{-1} (3) = x(3)$
So y = 3, solve for x

$f(x) = y = \frac{x+5}{3} \\ \\ \frac{x+5}{3} = 3 \\ \\ x+5 = 9 \\ \\ x = 4$

Therefore,
$f^{-1} (3) = 4$