![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step1.JPG\")
Method 1:
\List the factors of each number.
\Factors of 9: 3, 9.
\Factors of 15: 3, 5, 15.
\Identify the greatest common factor.
\The greatest common factor of 9 and 15 is 3.![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step2.JPG\")
Method 2:
\Write the prime factorization of each number.
\9 = 3 × 3.
\15 = 3 × 5.
\The GCF is the product of the common prime factors in each number.
\GCF = 3.
\The greatest common factor of 9 and 15 is 3.![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")
The greatest common factor of 9 and 15 is 3.