1) 1/2 - 2/5 = 5/10 - 4/10 = 1/10
2) 5/12 + 1/2 = 5/12 + 6/12 = 11/12
3) 4/5 - 2/3 = 12/15 - 10/15 = 2/15
4) 2/3 - 2/7 = 14/21 - 6/21 = 8/21
5) 3/4 - 3/8 = 6/8 - 3/8 = 3/8
6) 1/2 + 5/12 = 6/12 + 5/12 = 11/12
7) 2/3 + 1/6 = 4/6 + 1/6 = 5/6
8) 1/4 + 2/3 = 3/12 + 8/12 = 11/12
9) 1/3 - 1/7 = 7/21 - 3/21 = 4/21
10) 2/5 + 1/3 = 6/15 + 5/15 = 11/15