-8+(+9) = +(9-8) = +1+8+(-9) = +(8-9) = -1+12+(-15) = +(12-15) = -3-13+(+18) = +(18-13) = +5-2+(+18) = +(18-2) = +16+25+(-32) = +(25-32) = -7
-8+(+9) = +(9-8) = +1
+8+(-9) = +(8-9) = -1
+12+(-15) = +(12-15) = -3
-13+(+18) = +(18-13) = +5
-2+(+18) = +(18-2) = +16
+25+(-32) = +(25-32) = -7