Find the set $A \cup \varnothing$.
\[
\begin{array}{l}
U=\{1,2,3,4,5,6,7,8\} \\
A=\{3,4,6,7\}
\end{array}
\]

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Answer

Final Answer: $A \cup \varnothing = \boxed{\{3, 4, 6, 7\}}$

Steps

Step 1 ：Given the universal set $U = \{1,2,3,4,5,6,7,8\}$ and the set $A = \{3,4,6,7\}$.

Step 2 ：We are asked to find the union of set $A$ and the empty set.

Step 3 ：The union of a set with the empty set is always the set itself.

Step 4 ：Therefore, the union of set $A$ and the empty set is $A$ itself.

Step 5 ：Final Answer: $A \cup \varnothing = \boxed{\{3, 4, 6, 7\}}$