3/5 - 1/7 = (21-5) / 35 = 16/35
5/3 - 4/9 = (15-4) / 9 = 11/9
24/25 - 7/15 = (36-35) / 75 = 1/75
11/80 - 11/90 = (9-8) / 720 = 1/720
5 - 2 = 3
17 - 3 1/9 = 16 + 8/9 = 16 8/9
3/5 - 1/7 = (21-5) / 35 = 16/35
5/3 - 4/9 = (15-4) / 9 = 11/9
24/25 - 7/15 = (36-35) / 75 = 1/75
11/80 - 11/90 = (9-8) / 720 = 1/720
5 - 2 = 3
17 - 3 1/9 = 16 + 8/9 = 16 8/9