jmc

We know that $f(2)=9$. We can rewrite this as $f(-(-2))=9$, which shows that $(-2,9)$ must be on the graph of $y=f(-x)$. The sum of the coordinates of $(-2,9)$ is $\boxed{7}$.

Alternatively, note that the graphs of $y=f(x)$ and $y=f(-x)$ must be mirror images, with the $y$-axis being the axis of reflection. Thus, $(-2,9)$ is on the graph of $y=f(-x)$, and the sum of the coordinates of $(-2,9)$ is $\boxed{7}$.