1) 21-(5-8)=21-(-3)=21+3=24
2) 3.7-(4- 5.3)=3,7-(-1,3)=3,7+1,3=5
3) 1/6-(5/12-7/12)= 1/6 -(-2/12)=1/6+1/6=2/6=1/3
4) -13-(20-32)=-13-(-12)=12-13=-1
5) -4.5-(7- 9.5)=-4,5-(-2,5)=2,5-4,5=-2
6) -5/8-(5/8-1)= -5/8 - (-3/8) = 3/8-5/8 = -2/8=-1/4
7) -18-(9-5)= -18-4=-22
8) -0.25-(3- 2.25)= -0,25-0,75=-1
9) -2/9-(1- 8.9)= -2/9-7,9= -20/90 - 711/90= -731/90 = -8 целых 11/90