Пошаговое объяснение:

№5

-1 7/9 + (-2 11/12) = -(1 7/9 + 2 11/12) =

-(1 28/36 + 2 33/36) = -3 61/36 = -4 25/36

№6

6 1/6 + (-2 2/7) = 6 1/6 - 2 2/7 =

6 7/42 - 2 12/42 = 5 49/42 - 2 12/42 = 3 37/42