1) 1/2 + 7/12 = 6/12 + 7/12 = 13/12 = 1 целая 1/12
2) 2/5 + 3/7 = 14/35 + 15/35 = 29/35
3) 3/4 + 1/8 = 6/8 + 1/8 = 7/8
4) 2/7 + 1/2 = 4/14 + 7/14 = 11/14
5) 14/15 ?
6) 1/3 - 5/18 = 6/18 - 5/18 = 1/ 18
7) 1/2 - 3/20 = 10/20 - 3/20 = 7/20
8) 1/7 - 1/10 = 10/70 - 7/70 = 3/70