2/9 + 1/2 = 4/18 + 9/18 = 13/18
7/15 + 4/5 = 7/15 + 12/15 = 19/15 = 1 4/15
4/9 + 1/6 = 8/18 + 3/18 = 11/18
2/3 - 3/5 = 10/15 - 9/15 = 1/15
5/12 - 1/3 = 5/12 - 4/12 = 1/12
7/12 - 2/9 = 21/36 - 8/36 = 13/36
2/9 + 1/2 = 4/18 + 9/18 = 13/18
7/15 + 4/5 = 7/15 + 12/15 = 19/15 = 1 4/15
4/9 + 1/6 = 8/18 + 3/18 = 11/18
2/3 - 3/5 = 10/15 - 9/15 = 1/15
5/12 - 1/3 = 5/12 - 4/12 = 1/12
7/12 - 2/9 = 21/36 - 8/36 = 13/36