Answer:
2- 1/10=0.1; closest to zero
3- (25-4)/40= 21/40 (common denominator)
4- 12
5- (20-9)/24= 11/24 (common denominator)
6- (6+3/4) + (2+1/2) = 8+5/4= 9+1/4
7- 21+3/4 - 13+1/8 = (21-13)+(6/8-1/8) = 8+5/8
8- 8+5/12 - 5+3/8 = (8-5) + (10/24-9/24) = 3+1/24
9- 20