a)
8+(-6)+(4-5) = 8-6+(-1) = 2-1 = 1
-3-(+2)-(-3-4) = -3-2 -(-7)= - 5 + 7 = 2
+9+(-2+6)-(-7) = 8 + 4+7 = 12+7=19
-(-3)-(2-7)+(-6) = 3-(-5) - 6 = 3+5-6=8-6=2
12+(-8-5)-(4-7) = 12+(-13)-(-3) = -1 +3 = 2
-(+8)-(-2+9)+(-5+2) = -8 -(+7)+(-3) = 1-3 = -2
-(-4-2)+(-8+9)-(+13) = -(-6)+(+1)-13 = 7-13= - 6
b)
10+(+4)+(-1+5)-(-9-3) = 14 + 4 - (-12) = 18 + 12 = 30
-8+(-6)-(-3-8)+(+2) = -14-(-11)+2 = -3+2=-1
+7-(-3+11)+(-9+7)-(-4) = 7-(+8)+(-2)+4 = 1-2+4=-1+4=3
15+(-2-8)-(-3+8)+(-6) = 15 +(-10)-(+5)-6 = 5-5-6=-6
-(-9+3)+(-7)-(-2+3) = -(-6)-7-(+1) = 6-7+1= -1+1=0
8-(-9-8)+(+11)+(5-7) = 8-(-17)+11+(-2) = 25+11-2 = 36-2=34
-10+(-3)-(-9+2)-(-3+1) = -10-3-(-7)-(-2) = -13+7+2= - 6+2= - 4
