Ответ:

1. 6 2/3 + 2 3/5 = 6 10/15 +2 9/15(приводим к общему знаменателю) = 9 4/15

2. 15 2/6 + 4 3/7 = 15 14/42 + 4 18/42 = 19 32/42 = 19 16/21

3. 12 3/8 + 4 2/5 = 12 15/40 + 4 16/40 = 16 31/40

4. 16 2/9 + 4 3/4 = 16 8/36 + 4 27/36 = 20 35/36