What is the sum of 9 and 21?

What does it mean when someone asks you for the sum of 9 and 21? The sum is part of the addition equation displayed below.

addend + addend = sum

When someone asks "What is the sum of 9 and 21?" they mean that 9 is an addend and 21 is an addend in an addition equation.

Therefore, as you may have inferred, the sum of 9 and 21 is the same as 9 plus 21. Here is the addition equation with the answer:

9 + 21 = 30

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What is the sum of 9 and 22?
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