5/9 - 4/9 = (5-4)/9 = 1/9
11/21 - 9/21 = (11-9)/21 = 2/21
5/19 - 1/19 = (5-1)/19 = 4/19
7/8 - 6/8 = (7-6)/8 = 1/8
12/7 - 5/7 = (12-5)/7 = 7/7 = 1
9/16 - 9/16 = (9-9)/16 = 0/16 = 0
24/25 - 6/25 = (24-6)/25 = 18/25
68/81 - 51/81 = (68-51)/81 = 17/81
