The concept of common factors makes no sense for fractions. This is because every non-zero fraction can divide every other fraction. For example 27/4 = 5/7*189/20 and 9/16 = 5/7*63/80 so 5/7 is a common factor.
The GCF is 1.
The common factors of 4 and 16 are 1, 2, and 4.
The GCF is 4.
The GCF is 4.
The GCF is 4.
The GCF is 4.
The GCF of 16 and 72 is 8. 16/72 can be reduced to 2/9
The GCF is 16.
The GCF is 4.
The GCF is 4.
The GCF is 1.
The GCF is 4.