Finds the gcf of 18a, 20ab, and 6ab.

could you show your work? that would be awesome.

Segregate the coefficients and variables for a moment.

For the coefficients,
the factors of 18 are 1, 2, 3, 6, 9, and 18;
the factor of 20 are 1, 2, 4, 5, 10, and 20;
the factor of 6 are 1, 2, 3, and 6.

The "common factors" of these 3 numbers are 1 and 2.
Since 2 is greater than 1, the GCF is 2.

For variables, identify the smallest value of degree (or exponent) of "like" variables to get the GCF. Because the given monomials do not have a degree and also 8a doesn't have variable "b", automatically the GCF is a.

Multiplying together for the final GCF yields 2a. That is the answer.