Пошаговое объяснение:
1)
2 5/12 + 5 5/12 = (2 + 5) + (5/12 + 5/12) = 7 + 10/12 = 7 + 5/6 = 7 5/6,
2)
5 1/3 + 2 = (5 + 2) + 1/3 = 7 + 1/3 = 7 1/3,
3)
3 2/9 + 5 5/9 = (3 + 5) + (2/9 + 5/9) = 8 + 7/9 = 8 7/9,
4)
8 8/11 - 5/11 = 8 + (8/11 - 5/11) = 8 + 3/11 = 8 3/11