1.+21+22=22 -(+21)= -1
2.+15 - 21 = -21-15=-6
3.+18-(-5)=18+5=+23
4.-24 +(-5)=--29
5.-20-(+9)=-11
6. -9-10+15-20+1-5-8=-(19+(-5+-4+(-8=-36
7. -20+40-20-40-15=-35
8. -2-(-5)+(-8)-(+9)=-6
9. -8+(-6)-(+8)-(+9)=+3
10. 8-(-6)-(-2)-(-21)=-37
11. (-9)-(-1)+(+9)+(-10)=