(-9)-(-13)+(-20)+(-2)=-9+13-20-2
3+13-(-7)+6
=3+13+7+6
(-2)-8-14-13=-2-8-14-13
(-7)+(-5)-(-8)+3= -7-5+8+3
(-11)-4-(-18)+18
=-1-4+18+18
4+(-11)-1-(-3)
=4-11-1+3
(-17)-6-16-(-18)
=-17-6-16+18
5+7+(-1)-(-8)
=5+7-1+8
(-1)-(-1)+15+1
=-1+1+15+1
3-(-5)-3+(-15)
=3+5-3-15
6+(-14)-(-14)+(-13)
=6-14+14-13
(-15)-(-13)-(-17)-(-4)
=-15+13+17+4
(-20)-13+(-7)+11
=-20-13-7+11
8+(-1)-7+(-4)
=8-1-7-4
(-13)-(-9)+16-(-12)
=-13+9+16+12
