What is the greatest common factor of 15 and 24?

The greatest common factor of 15 and 24 is three.

The factors of 15 are 1, 3, 5, and 15

The factors of 24 are 1, 2, 3, 4, 6, 8, 12, and 24

The highest common factor of 15 and 24 is 3

You are left with 8 and 3 respectively. The numbers cannot be further reduced, thus three is the GCF.
The GCF is 3.
The GCF is 3.
3.
The GCF is 3.
The GCF is 3.