Answer: 8
Step-by-step explanation: The factors of 40 are: 1, 2, 4, 5, 8, 10, 20, 40
The factors of 72 are: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72
This means the greatest common factor is 8.
