4 will be your answer
Explanation:
The factors of 12 are 1, 2, 3, 4, 6, 12
The factors of 88 are 1, 2, 4, 8, 11, 22, 44, 88.
So, as we can see, the Greatest Common Factor or Divisor is 4, because it is the greatest number that divides evenly into all of them.
hope it helped :D