List the factors for 21 and List the factors for 35, then list the Common factors and Greatest Common Factor for 21 and 35

The factors of 21 are: 1, 3, 7, 21.

The factors of 35 are: 1, 5, 7, 35.
The common factors of 21 and 35 are: 1, 7.
The greatest common factor of 21 and 35 is: 7.