Ответ:

Пошаговое объяснение:

А) 2 7/9+4 2/3  = 6 + (7/9 + 6/9) = 6 + 13/9 = 6 + 1 4/9 = 7 4/9

4 2/15-1 5/21  = 3 + (2/15 - 5/21) = 3 + (14/105 - 25/105) = 3 + (-11/105) = 315/105 - 11/105 = 304/105

Б)5 3/8+1 2/7  = 6 + (3/8 + 2/7) = 6 + (21/56 + 16/56) = 6 + 37/56 = 6 37/56

3 11/45-2 13/30  = 1 + (11/45 - 13/30) = 1 + (22/90 - 39/90) = 1 + (-17/90) = 90/90 - 17/90 = 73/90

В)3 7/12+7 9/20  = 10 + (7/12 + 9/20) = 10 + (35/60 + 27/60) = 10 + 62/60 = 11 + 2/60 = 11 1/30

Г)7 9/24-3 19/36 = 4 + (9/24 - 19/36) = 4 + (27/72 - 38/72) = 4 + (-11/72) = 3 72/72 - 11/72 = 3 61/72