Пошаговое объяснение:
1) 7 7/8 + 6 6/8 = 13 13/8 = 14 5/8
2) 1 - 5/8 = 8/8 - 5/8 = 3/8
3) 12 - 4/19 = 11 19/19 - 4/19 = 11 15/19
