7/15 + 8/15 = 15/15 = 1
1 - 28/60 = 60/60 - 28/60 = 32/60 = 8/15
1 - 8/80 = 80/80 - 8/80 = 72/80 = 9/10
7/15 + 8/15 = 15/15 = 1
1 - 28/60 = 60/60 - 28/60 = 32/60 = 8/15
1 - 8/80 = 80/80 - 8/80 = 72/80 = 9/10