How to find s?
Of course, it is not impossible if you know what you are doing.
Here is a start.
Let $\displaystyle S=\left( {s_x ,s_y } \right)$. Then $\displaystyle T$ is the midpoint of the diagonal so:
$\displaystyle T=\left( {\frac{{s_x +9}}{2},\frac{{s_y + 3}}{2}} \right)$ solve for $\displaystyle s_x~\&~s_y$.
Then $\displaystyle \overleftrightarrow {PR} = P + t\overrightarrow {PT} $
Now you do some work.