The GCF of 28 and 64 is "4" or the second option.
The factors of 28 are 28, 14, 7, 4, 2, 1.
The factors of 64 are 64, 32, 16, 8, 4, 2, 1.
As you can see the highest the numbers go is 4 therefore 4 is your answer.
Hope this helps!
~Nonportrit
