1. 9 1/4-8 2/3)·10-2 1/2 ∶3 3/4+ (2 1/2-1 1/3)·6
2. 1 5/7+(4 2/9-2 5/6) ∶1 1/9
3. 2 3/11· 7/9+6· 8/11 ∶1 2/7-1 16/99