#### Answer

$-9$

#### Work Step by Step

$a+9=15$
$a+9+(-9)=15+(-9)$
$a=6$

Published by
Pearson

ISBN 10:
0321726391

ISBN 13:
978-0-32172-639-1

$-9$

$a+9=15$
$a+9+(-9)=15+(-9)$
$a=6$

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