Find the CGF of 78 and 86

To find the common greatest factor (CGF) of 78 and 86, we need to find all the factors of each number and see which ones they have in common.

The factors of 78 are: 1, 2, 3, 6, 13, 26, 39, 78.

The factors of 86 are: 1, 2, 43, 86.

The factors these numbers have in common are: 1 and 2.

Therefore, the CGF of 78 and 86 is 2.