Question: what are the common prime factors of 12 and 16?
Answer: The prime factorization of 12 is: 2 x 2 x 3. The prime factorization of 16 is: 2 x 2 x 2 x 2. The prime factors and multiplicities 12 and 16 have in common are: 2 x 2. 2 x 2 is the gcf of 12 and 16.