The greatest common factor is the largest number that is a factor of all 3 numbers.
16s^3t, 40s^5, and 68t^2
In this case, we don't even need to worry about the variables because they do not occur in all 3 numbers.
Let's worry about the coefficients:
16, 40, and 68
Let's try to divide each number by 4.
16 / 4 = 4
40 / 4 = 10
68 / 4 = 17
Since 17 is prime, 4 is the largest factor of each number. Therefore, the GCF of the three expressions above is 4.
