3 2/13 - 4/13 = 3 2/13 - 1/13 = 3 1/13
4 4/15 - 2 7/15 = 4 + 4/15 - 2 - 7/15 = 2 + 4/15 - 7/15 = 2 - 3/15 = 2 - 1/5 = 1 4/5
3 2/13 - 4/13 = 3 2/13 - 1/13 = 3 1/13
4 4/15 - 2 7/15 = 4 + 4/15 - 2 - 7/15 = 2 + 4/15 - 7/15 = 2 - 3/15 = 2 - 1/5 = 1 4/5