481.
1) 2 7/9 - 1/3 = 2 7/9 - 3/9 = 2 4/9
2) 3 4/5 - 2/3 = 3 12/15 - 10/15 = 3 2/15
3) 4 5/6 - 2 1/3 = 4 5/6 - 2 2/6 = 2 3/6 = 2 1/2
4) 6 4/5 - 2 3/8 = 6 32/40 - 2 15/40 = 4 17/40
5) 9 1/2 - 4 3/8 = 9 4/8 - 4 3/8 = 5 1/8
6) 8 19/20 - 5 7/10 = 8 19/20 - 5 14/20 = 3 5/20 = 3 1/4