The work that Ryan did to find the greatest common factor of 48 and 72 is shown below.

Prime factorization of 48: 2 x 2 x 2 x 2 x 3
Prime factorization of 72: 2 x 2 x 2 x 3 x 3

The greatest common factor is 2 ´ 2 ´ 2 ´ 3 x 3

What is Ryan’s error?