Find the coordinates of the other endpoint when you are given the midpoint (point m) and one of the endpoints (point p). p = (3, 5) and m =(-2, 0)

I'll try to explain. The trouble is that I do not know English :)
About Points
S = (x,y)        searched point (it will be in the third quadrant )
M = (-2,0)      Midpoint | SP |
P = (3,5)        one end of the segment | SP |

You have to draw Cartesian.

 we set in a point M and P. We both points by a simple and we extend it for the third quarter of the system. Compass measure the distance from the point M to the point P. From the point M we set a compass point S. Figure attached. Received point S = ( -7 , -5 ) . It sought a point that calculate .

We use the information that | SM | = | MP |





Answer : S = (-7,-5)

as soon as I had a good range will add drawing