Răspuns :
-18-2-{15-4-[10-(8-5)+(-3+9)]}=
-20-[11-(10-3+6)]=
-20-(11-13)=
-20-(-2)=
=-20+2
=-18
-20-[11-(10-3+6)]=
-20-(11-13)=
-20-(-2)=
=-20+2
=-18
-18-2-(15-4-(10-(8-5)+(-3+9)))
=-18-2-(15-4-(10-3+6))
=-18-2-(15-4-13)
=-18-2-(-2)
=-18-2+2
=-18
=-18-2-(15-4-(10-3+6))
=-18-2-(15-4-13)
=-18-2-(-2)
=-18-2+2
=-18