Respuesta:
Explicación paso a paso:
a) 11+{-5-[-1-(-2)+(-4-6)+6]-9}
11+{-5-[-1+2+(-10)+6]-9}
11+{-5-[-1+2-10+6]-9}
11+{-5-[-3]-9}
11+{-5+3-9}
11+{-11}
11-11
0
b) -8+{-21+[+8-(-8)]+13}
-8+{-21+[8+8]+13}
-8+{-21+16+13}
-8+{8}
-8+8
0
c) (15-21)-[+5-3-10-(9+1)]
-6-[-8-(10)]
-6-[-8-10]
-6+18
12
d) -{7-13-(-8)+[11-(-2-7)]+3}-2
-{-6+8+[11-(-9)]+3}-2
-{2+[11+9]+3}-2
-{2+[20]+3}-2
-{25}-2
-25-2
-27