1. The problem asks us to find the common factors of both 12 and 18. 2. First, find the factors of 12: 1, 2, 3, 4, 6, 12. 3. Next, find the factors of 18: 1, 2, 3, 6, 9, 18. 4. Identify the common factors by finding numbers that appear in both lists: 1, 2, 3, 6. 5. From the given options (2, 3, 6, 9, 12), the common factors are 2, 3, and 6. Final answer: The numbers that are common factors of both 12 and 18 are 2, 3, and 6.