If the point $(2,9)$ is on the graph of $y=f(x)$, then there is one point which must be on the graph of $y=f(-x)$. What is the sum of that point's coordinates?
$f(2)=9\implies f(-(-2))=9$, the point is $(-2,9)$ and the sum is $9-2=\boxed{7}$.