Answer:
16
Step-by-step explanation:
The greatest common factor is the greatest integer which divides evenly into both numbers. One way to find this is to list all of the divisors of one of the numbers, and then select the biggest of those that divides evenly into the other number, and that number is the greatest common factor.
We start with 64.
Its divisors are 1, 2, 4, 8, 16, 32, 64. The biggest of those numbers which divides evenly into 80 is 16.
Thus, the greatest common factor is 16.
