jmc

Let's say that the distance from the picture to the wall is $x$. Since that distance will be on both sides of the picture (it's in the exact middle), we can say that $$\begin{array}{rl}x+3+x=19& \Rightarrow 2x+3=19\\ & \Rightarrow 2x=16\\ & \Rightarrow x=8\end{array}$$ $\boxed{8}$