The answer is 270. Simply add up all of the numbers arithmetically like you would for two plus two. To make sure the answer is correct, check your work using a calculator.
15 + 12 + 17 = 44
17 plus 15 plus 13 equals 45.
17 + 25 + 15 = 57
55 + 34 + 31 + 27 + 21 + 21 + 20 + 17 + 15 + 15 = 256
3 + 11 + 11 + 11 + 12 + 13 + 15 + 15 + 16 + 17 + 19 = 143
-2 + 17 = 15
15 + 2 = 17
It is: 17+28+15 = 60
It is -17+2 = -15
-17.
It is: 15+(-32) = -17