You should use your calculator for such simple sums. It is far quicker and involves fewer key depressions. I could tell you that the answer is 207 but how can you be sure that I did not make a mistake? Or that I am not messing about?
-43 + 21 = -22
43
37 plus 43 equals 80.
To add 26 and 17 using the common core method with mental math, you can break the numbers into tens and ones. First, add the tens: 20 (from 26) plus 10 (from 17) equals 30. Next, add the ones: 6 (from 26) plus 7 (from 17) equals 13. Finally, combine the two results: 30 plus 13 equals 43. Thus, 26 plus 17 equals 43.
B=26 you just have to isolate the variable, so subtract 17 from 43 because the rule in algebra is that whatever you do to one side, you have to do to the other
89 plus 43 plus 37 equals 169.
19 + 43 + 13 = 75
25
16 plus 27 equals 43.
43
43
-17