Show how to make one addend the next tens number. 15+37=?

Using long addition to evaluate would give you 52. Adding by using long addition would also give you 52. If you simplify, your answer would still be 52.
=52

The answer is 15+37=52

38+105= 143, 39+104=143, and you will find then adding the numbers on opposite sides, moving inwards yields the answer 138 every time. because of this, you’re going to multiply 138 times the number of pairs, which is 34. therefore, 34*138= 4692(i’m sorry if it’s the wrong numbers, but it’s the right concept)