Respuesta :

GCF means: greatest common factor, the biggest number by which both numbers can be divided.

We knew that both numbers are divisible by 3: both 6 and 3 are divisible by 3.

also, they are both divisible by "a": since they are products of a and other numbers or variables.

So the answer is:

3a
GCF= 

Greatest common factor.

6a and 3a can both be divided by 3a

So our final answer: 

3a