2-8=-6
-18-(-12)=-18+12=-6
-24+13=-11
48-55=-7
-17-14=-17+-(-14)=-31
5-12=-7
-11-(-15)=-11+15=4
-4+3=-1
8-15=-7
-33-22=-33+(-22)=-55
12-27=-15
-21-(-11)=-21+11=-10
-25+17=-8
27-77=-50
-5-18=-5+(-18)=-23
6-12=-6
-89-(-13)=-89+13=-76
-23+13=-10
77-85=-8
-19-21=-19+(-21)=-40