Ответ:

4-4/7 = 4/1 - 4/7 = 28/7 - 4/7 = 24/7 = 3 3/7

8 - 2 1/4 = 8/1 - 9/4 = 32/4 - 9/4 = 23/4 = 5 3/4

2 3/4 - 1/2 = 11/4 - 1/2 = 11/4 - 2/4 = 9/4 = 2 1/4

6 1/4 + 2 1/2 = (6+2) 1/4 + 1/2 = 8 1/4 + 2/4 = 8 3/4