78 plus what equals 87?

This is how to calculate "78 plus what equals 87?" In other words, 78 plus a number equals 87. What is that number? We start by converting this word problem into an equation where "what" is what we want to solve:

78 + what = 87

To solve this equation, we first add -78 to each side of the equal sign like this:

78 - 78 + what = 87 - 78

Then, we do the calculation to get the answer to "78 plus what equals 87?" as follows:

What = 9

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

Plus What Equals Calculator
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78 plus what equals 88?
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