15 plus what equals 12?

This is how to calculate "15 plus what equals 12?" In other words, 15 plus a number equals 12. What is that number? We start by converting this word problem into an equation where "what" is what we want to solve:

15 + what = 12

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

15 - 15 + what = 12 - 15

Then, we do the calculation to get the answer to "15 plus what equals 12?" as follows:

What = -3

The answer to "15 plus what equals 12?" is -3. You know this answer is correct because 15 plus -3 equals 12.

Plus What Equals Calculator
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