30 plus what equals 15?

This is how to calculate "30 plus what equals 15?" In other words, 30 plus a number equals 15. What is that number? We start by converting this word problem into an equation where "what" is what we want to solve:

30 + what = 15

To solve this equation, we first add -30 to each side of the equal sign like this:

30 - 30 + what = 15 - 30

Then, we do the calculation to get the answer to "30 plus what equals 15?" as follows:

What = -15

The answer to "30 plus what equals 15?" is -15. You know this answer is correct because 30 plus -15 equals 15.

Plus What Equals Calculator
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