Explanation
The union of two sets is a set containing all elements that are in A or in B (possibly both)
hence
to find the answer we need to check the elements present inboth sets,
Step 1
Let
[tex]\begin{gathered} A=\lbrace2,3,7\rbrace \\ B=\lbrace3,7,8\rbrace \end{gathered}[/tex]hence
[tex]\begin{gathered} A\cup B=\lbrace3,7\rbrace \\ \end{gathered}[/tex]therefore, the answer is
[tex]\lbrace3,7\rbrace[/tex]I hope this helps you
