8/15 minus 7/20 is 11/60
5/6 − 3/10 = 8/15
21/30 - 8/30 = 13/30
3/2 - 7/10 = 15/10 - 7/10 = 8/10 = 4/5
9/10 minus 7/8 is 1/40
8/15 − 2/5 = 2/15
4/5 - 8/15 = 12/15 - 8/15 = 4/15
8/15 - 3/15 = 5/15 or 1/3
21/30 - 5/30 = 16/30 = 8/15
1/8 - 1/15 = (1*15 - 8*1)/8*15. The answer is 7/120.
11/15 - 3/15 = 8/15
8/11 − 4/15 = 76/165