Question: what is greatest common factor of 3 and 6?
Answer: The factors of 3 are 3, 1. The factors of 6 are 6, 3, 2, 1. The common factors of 3 and 6 are 3, 1, intersecting the two sets above. In the intersection factors of 3 ∩ factors of 6 the greatest element is 3. Therefore, the greatest common factor of 3 and 6 is 3.