90 plus what equals 1?

This is how to calculate "90 plus what equals 1?" In other words, 90 plus a number equals 1. What is that number? We start by converting this word problem into an equation where "what" is what we want to solve:

90 + what = 1

To solve this equation, we first add -90 to each side of the equal sign like this:

90 - 90 + what = 1 - 90

Then, we do the calculation to get the answer to "90 plus what equals 1?" as follows:

What = -89

The answer to "90 plus what equals 1?" is -89. You know this answer is correct because 90 plus -89 equals 1.

Plus What Equals Calculator
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