The greatest common factor is 2
We first have to look for the largest number that goes into both equations. The factors of 12 are 1, 2, 3, 4, 6 and 12. None of 3, 4, 6, or 12 go into 26 evenly. So 2 is the largest number you can take out.
With the variables, we take out as many as the lowest number will let us. Since the smallest number of n's is 2 in the second term, we take that many.