What plus 8 equals 21?

This is how to calculate "What plus 8 equals 21?" In other words, what do you add to 8 to get 21? We start by converting this word problem into an equation where "What" is what we want to solve:

What + 8 = 21

To solve this equation, we first add -8 to each side of the equal sign like this:

What + 8 - 8 = 21 - 8

Then, we do the calculation to get the answer to "What plus 8 equals 21?" as follows:

What = 13

The answer to "What plus 8 equals 21?" is 13. You know this answer is correct because 13 plus 8 equals 21.

What Plus Calculator
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What plus 8 equals 22?
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