what is a greatest common factor of 80 and 20?
['The prime factorization of 20 is: 2 x 2 x 5.', 'The prime factorization of 80 is: 2 x 2 x 2 x 2 x 5.', 'The prime factors and multiplicities 20 and 80 have in common are: 2 x 2 x 5.', '2 x 2 x 5 is the gcf of 20 and 80.', 'gcf(20,80) = 20.']