In a given line XY the midpoint is (5, 7) . The one endpoint X is (- 2, 8) . Find the other Endpoint Y?

If M is the midpoint,

M-X = Y-M
So, for the x-coordinate,
5-(-2) = x-5
x = 12
check: -2+7=5, 5+7=12

Do y in like wise.