31 plus what equals 40?

This is how to calculate "31 plus what equals 40?" In other words, 31 plus a number equals 40. What is that number? We start by converting this word problem into an equation where "what" is what we want to solve:

31 + what = 40

To solve this equation, we first add -31 to each side of the equal sign like this:

31 - 31 + what = 40 - 31

Then, we do the calculation to get the answer to "31 plus what equals 40?" as follows:

What = 9

The answer to "31 plus what equals 40?" is 9. You know this answer is correct because 31 plus 9 equals 40.

Plus What Equals Calculator
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31 plus what equals 41?
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