Пошаговое объяснение:

№1

3 4/9 + 7 8/9 = 10 12/9 = 11 3/9 = 11 1/3

8 7/13 - 4 9/13 = 7 20/13 - 4 9/13 = 3 11/13

5 1/4 + 6 3/4 = 11 4/4 = 12

№2

3 2/5 - 4/5 = 2 7/5 - 4/5 = 2 3/5

13 3/7 + 5/7 = 13 8/7 = 14 1/7

11 8/17 - 20/17 = 10 25/17 - 20/17 = 10 5/17

№3

1) 5 5/12 - 3 7/12 = 4 17/12 - 3 7/12 = 1 10/12

2) 1 10/12 + 11/12 = 1 21/12 = 2 9/12 = 2 3/4