For this case we have that by definition, the GCF of two numbers is the biggest factor that divides both numbers without leaving any residue. So, we find the factors of 12 and 9:
12: 1,2,3,4,6,12
9: 1,3,9
Thus, the GFC of both is 3.
So, we have:
![3x (4x-3)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/zpdehpy4bzsg0001sfd35bt06yept5vfw3.png)
Answer:
GFC: 3x