Question 467843
The equation you would use would be the midpoint formula, 

((x1 + x2/ 2), (y1 +  y2 / 2)) = midpoint.

(( 0 +  x2 )/ 2 ) = 4
x2 = 8.

((13 + y2 )/ 2  ) = -6
y2 = -25.
The second point R is (8, -25).
Cleomenius.