The greatest common factor is B) 3x^2.
In order to find this, we must first look to see the smallest number of x's in a term. The final term 6x^2 (which could also be expressed as 6xx), has 2. Therefore we know we can take out x^2.
The next thing we look for is a number that goes in evenly to all terms. It's easiest to start with the smallest number and it's factors. 6 is the smallest number and it's factors are 6, 3, 2, 1.
Since 6 does not go in evenly to 27, we try 3. 3 goes in evenly to both 27 and 12. Therefore, we can use 3.
The end result is 3x^2