Question 53138
Add the X points and divide by 2
Add the Y points and divide by 2

Assuming that you have two points (2,4) and (-5,-8) in the cartesian coordinates, the midpoint is found as follow:
Midpoint of X = (2 + (-5))/2 = (2- 5)/2 = -3/2
Midpoint of Y = (4 + (-8))/2 = (4-8)/2 = -4/2 = -2

the midpoint is (-3/2, -2).