4 = 2 * 2
12 = 2 * 2 * 3
18 = 2 * 3 * 3
The least common multiple (LCM) is like a parts list with enough parts to make 4, 12, or 18. In this case that's 2 * 2 * 3 * 3 because that's enough parts to make 4, 12, or 18.
2 * 2 * 3 * 3 = 36
Answer: The LCM is 36.