Answer
$f^{-1} (0)$ = 1
$f^{-1} (4)$ = 3
Work Step by Step
For this graph, each value of x has one unique value of y, so the graph of this function $f$ has an inverse.
From the graph, $f(x)$ hits the following integer points: $(0, -1) (1, 0 ) (3, 4) (4,5) (6,7)$
To find $f^{-1} (0)$, determine the point that has 0 as a y-coordinate (since inverse switches x and y). In this case, it is (1,0), so $f^{-1} (0) = 1$
Thus, $f^{-1} (4) = 3$ since $f(x)$ contains the point (3,4)