Problem
(3) Let $A=\{4,5,6,8\}$ and $B=\{3,5,7,8\}$, and ask: $A \cup B$.
Solution
Step 1 ：Let $A=\{4,5,6,8\}$ and $B=\{3,5,7,8\}$, and ask: $A \cup B$.
Step 2 ：The question is asking for the union of sets A and B. The union of two sets is a set containing all the elements of both sets.
Step 3 ：Perform the union operation on sets A and B.
Step 4 ：Final Answer: $A \cup B = \boxed{\{3, 4, 5, 6, 7, 8\}}$
