1)21-(5-8)=21-(-3)=24
2)3,7-(4-5,3)=3,7-(-1,3)=5
3)1/6-(5/12-7/12)=1/6-(-2/12)=2/12+2/12=4/12=1/3
4)-13-(20-32)=-13-(-12)=-13+12=-1
5)-4,5-(7-9,5)=-4,5-(-2,5)=-4,5+2,5=-2
6)-5/8-(5/8-1)=-5/8+8/8-5/8=-5/8+3/8=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-(9/9-8/9)=-2/9-1/9=-3/9=-1/3