The GCF is 21.
The greatest common factor of 18 21 and 42 is 3.
The GCF is 3.
The GCF of 18 and 42 is 6. The GCF of 42 and 56 is 14.
The GCF is 21.
The GCF is 21.
The GCF is 21.
The GCF is 3.
Since 21 is a factor of 42, it is automatically the GCF.
The GCF of 21 and 42 is 21. The GCF of 17 and 27 is 1.
The GCF is 6.
The GCF is 6.