1/2 + 3/5 - 2/3 = 15/30 + 18/30 - 20/30 = (15 + 18 - 20) / 30 = 13/30
5/9 + 1/6 + 3/4 = 20/36 + 6/36 + 27/36 = (20 + 6 + 27) / 36 = 53/36
1/4 + 1/5 - 3/10 = 10/40 + 8/40 - 12/40 = (10 + 8 - 12) / 40 = 6/40 = 3/20
1/2 + 3/5 - 2/3 = 15/30 + 18/30 - 20/30 = (15 + 18 - 20) / 30 = 13/30
5/9 + 1/6 + 3/4 = 20/36 + 6/36 + 27/36 = (20 + 6 + 27) / 36 = 53/36
1/4 + 1/5 - 3/10 = 10/40 + 8/40 - 12/40 = (10 + 8 - 12) / 40 = 6/40 = 3/20