Answer:
[tex]\Huge \boxed{-3}[/tex]
Step-by-step explanation:
To solve this problem, first you have to use add & subtract integers from left to right. Additive inverse is a opposite of a number. Additive inverse are the same distance from zero. The absolute value are the same.
First, add & subtract numbers from left to right.
[tex]\displaystyle -21+18=-3[/tex]
Therefore, the correct is -3.
Hope this helps!
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