You need at least two numbers to find a GCF.
The GCF is 4.
Since 72 is a factor of 144, it is automatically the GCF.
Since 18 is a factor of 72, it is automatically the GCF.
Since 72 is a factor of 144, it is automatically the GCF of this problem.
The GCF is 12.
The GCF is 7.
The GCF is 12.
The common factors of 72 and 123 are: 1 and 3
The common factors of 72 and 86 are: 1 and 2
Common factors of 28 and 42 are: 1, 2, 7, and 14.
2 and 4 are factors of 8. If you want them to be common, you need to compare them to another set of factors.
Common factors of 81 and 72 are: 1, 3, and 9.