87 plus what equals 9?

This is how to calculate "87 plus what equals 9?" In other words, 87 plus a number equals 9. What is that number? We start by converting this word problem into an equation where "what" is what we want to solve:

87 + what = 9

To solve this equation, we first add -87 to each side of the equal sign like this:

87 - 87 + what = 9 - 87

Then, we do the calculation to get the answer to "87 plus what equals 9?" as follows:

What = -78

The answer to "87 plus what equals 9?" is -78. You know this answer is correct because 87 plus -78 equals 9.

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87 plus what equals 10?
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