15/56
Пошаговое объяснение:
1) 1 1/4 * 2 2/7 = 5/4 * 16/7 = 20/7 = 2 6/7
2) 2 2/7 + 2 6/7 = 4 8/7 = 5 1/7
3) 5 1/7 - 4 7/8 = 5 8/56 - 4 49/56 = 15/56
