Find the other endpoint of the line segment with the given endpoint and midpoint.
67) Endpoint: (-7, -1), midpoint: (-2, 1)
68) Endpoint: (-3, 8), midpoint: (1,7)
69) Endpoint: (1,4), midpoint: (6, 9)
70) Endpoint: (3,9), midpoint: (3, 3)
71) Endpoint: (10, -9), midpoint: (0, -10)
72) Endpoint: (-1,-1), midpoint: (6,4)
