1. **State the problem:** Find the union of sets A and B, where Set A = factors of 12, Set B = factors of 10. 2. **Identify the factors:** - Factors of 12 are $\{1, 2, 3, 4, 6, 12\}$ - Factors of 10 are $\{1, 2, 5, 10\}$ 3. **Formula for union:** $$A \cup B = \{x | x \in A \text{ or } x \in B\}$$ 4. **Find the union:** Combine all unique elements from both sets: $$A \cup B = \{1, 2, 3, 4, 5, 6, 10, 12\}$$ 5. **Answer:** The union is $\{1, 2, 3, 4, 5, 6, 10, 12\}$. 6. **Count the intersection elements:** Intersection $A \cap B$ contains elements common to both sets: $$A \cap B = \{1, 2\}$$ Number of elements in $A \cap B$ is 2. 7. **Summary:** - $A \cup B = \{1, 2, 3, 4, 5, 6, 10, 12\}$ - $|A \cap B| = 2$