Answer
$\{1,2,3,7,8\}$
Work Step by Step
Our goal is to find the union of the two given sets:
$\{1,3,7,8\}\cup \{2,3,8\}$
To find the union, we first list the elements of the first set: $1,3,7,8$. Next, we list the elements of the second set: $2,3,8$. We write the elements common to both sets: $1,2,3,7,8$. Note that we do not repeat any elements, even if they appear in both sets. The result is the union:
$\{1,3,7,8\}\cup \{2,3,8\}=\{1,2,3,7,8\}$
