#### Answer

$\{1,2,5,a\}$

#### Work Step by Step

Recall that the union of two sets is the set of all elements that are contained in either of the sets. Thus, $\{1,2,5\}\cup\{5,a\}=\{1,2,5,a\}$.

Published by
Pearson

ISBN 10:
0-13446-914-3

ISBN 13:
978-0-13446-914-0

$\{1,2,5,a\}$

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