Find the difference between the midpoint and the known endpoint by subtracting the X and Y values from each other:
X: 10 - 6 = 4
Y: 7 - 4 = 3
Now add those values to the midpoint to find the other endpoint:
X: 10 +4 = 14
Y: 7 +3 = 10
Endpoint = (14,10)
