What is the greatest common factor of 9 and 15?

The greatest common factor of 9 and 15 is 3.

To find the greatest common factor between two numbers, you can identify all the factors of each number and then determine the largest number that both numbers have in common.

For 9, the factors are 1, 3, and 9. For 15, the factors are 1, 3, 5, and 15.

The largest number that is common between the two numbers is 3, so the greatest common factor of 9 and 15 is 3.