A)[-18-(-15-22)-1]-[-24-(-45)]=
=[-18-(-37)-1]-(-24+45)=
=(-18+37-1)-21=
=18-21=-3
B)[+7-(25-68)]+[-14-(9+7)]=
=[+7-(-43)]+(-14-16)=
=(+7+43)+(-30)=
=+50-30=+20
C){-2-[7+(-3-18)-(-12)]-20}-15=
={-2-[7+(-21)+12]-20}-15=
=[-2-(7-21+12)-20]-15=
=(-2+2-20)-15=-20-15=-35
D)-17-{-16-[-15-(-14)]+13}-12=
=-17-[-16-(-15+14)+13]-12=
=-17-(-16+1+13)-12=
=-17+2-12=-27
