Since you don't provide the coordinates of the point W, I will help you in a general form anyway. In the Figure below is represented the segment that matches this problem. We have two endpoints U and V. So, by using the midpoint formula we may solve this problem:
[tex] Midpoint=W=W(\frac{x_{1}+x_{2}}{2}, \frac{y_{1}+y_{2}}{2})=W(x_{3}, y_{3}) \\ \\ where:\\ \ U=U(x_{1}, y_{1}) \ and \ V=V(x_{2}, y_{2}) \\ \\ and: \\ x_{3}=\frac{x_{1}+x_{2}}{2} \\ y_{3}=\frac{y_{1}+y_{2}}{2} [/tex]
Therefore:
[tex] x_{2}=2x_{3}-x_{1} \\ y_{2}=2y_{3}-y_{1} [/tex]
So we know [tex]x_{3} \ and \ y_{3}[/tex] but we also must know [tex]x_{1} \ and \ y_{1}[/tex]
Finally, knowing the points U and W we can find the endpoint V.
