To find the greatest common factor, line both numbers up and continue adding that specific number until you find two factors that correlate with both numbers.
With that being said, let's begin.
8: 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88
Simply add 8.
11: 11, 22, 33, 44, 55, 66, 77, 88
Simply add 11.
The greatest common factor of 8 and 11 is 88.