15 plus what equals 57?

This is how to calculate "15 plus what equals 57?" In other words, 15 plus a number equals 57. What is that number? We start by converting this word problem into an equation where "what" is what we want to solve:

15 + what = 57

To solve this equation, we first add -15 to each side of the equal sign like this:

15 - 15 + what = 57 - 15

Then, we do the calculation to get the answer to "15 plus what equals 57?" as follows:

What = 42

The answer to "15 plus what equals 57?" is 42. You know this answer is correct because 15 plus 42 equals 57.

Plus What Equals Calculator
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