x = 15 is in fact a solution of the given inequality.
Here we have the inequality:
x + 9 > 21
We want to see if it is true for x = 15, to check it, we need to repace the value:
15 + 9 > 21
24 > 21
This is true, 24 is larger than 21, then we conclude that x = 15 is a solution of the given inequality.
If you want to learn more about inequalities you can read:
https://brainly.com/question/18881247
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