Verified answer

Пошаговое объяснение:

-2/7 + 1/7 = -(2/7 - 1/7) = -1/7

3/7 + (-6/7) = 3/7 - 6/7 = -(6/7 - 3/7) = -3/7

7/12 + (-3/4) = 7/12 - 3/4 = 7/12 - 9/12 = -(9/12 - 7/12) = -2/12 = -1/6

-3/8 + 1/4 = -3/8 + 2/8 = -(3/8 - 2/8) = -1/8