Answer
$f^{-1}(-3)=-2$
Work Step by Step
The inverse of a function differs from the original function in that all the x-coordinates and y-coordinates have been switched.
To find the value of $f^{-1}(-3)$, we have to find the corresponding x-coordinate to $y=-3$ in the original $f(x)$ function and switch the coordinates.
We can see, that in the graph of $f(x)$, when $y=-3$, the value of $x$ is $x=-2$.
Therefore $f^{-1}(-3)=-2$.