4/15 + 3/5 = 4/15 + 9/15 = 13/15
3/8 + 7/20 = 15/40 + 14/40 = 29/40
3/16 + 1/24 = 9/48 + 2/48 = 11/48
1 9/14 + 2 1/7 = 2 + (9/14 + 1/7) = 2 + (9/14 + 2/14) = 2 + 11/14 = 2 11/14
1 5/8 + 2 9/16 = 3 + (5/8 + 9/16) = 3 + (10/16 + 9/16) = 3 + 19/16 = 4 3/16
7/10 - 1/2 = 7/10 - 5/10 = 2/10 = 1/5
13/20 / 3/8 = 26/40 - 15/40 = 11/40