['The prime factorization of 12 is: 2 x 2 x 3.', 'The prime factorization of 66 is: 2 x 3 x 11.', 'The prime factors and multiplicities 12 and 66 have in common are: 2 x 3.', '2 x 3 is the gcf of 12 and 66.', 'gcf(12,66) = 6.']