20 + 12 + 32 + 20 + 30 + 72 = 186
25+16+12+42+20=115
5 + 8 + 20 + 12 + 19 = 64
12 + 16 + 18 + 20 + 9 = 75
-20
8 + 12 = 20
10 + 12/3 + 20 = 34
20 + 10 - 12 = 18
-6 + 12 - 20 = 6 - 20 = -14
Addition is commutative. That is, a + b = b + a for all a, b
20
20 + 12 - 8 = 24