The greatest common factor (GCF) of 9, 21 and 60 is: 3
Factors of 9: 1, 3, 9
Factors of 21: 1, 3, 7
Factors of 60: 1, 2, 3, 4, 5, 6
The common factors between the three numbers are 1 and 3, but since 3 is the highest number, it is considered the GCF.
