Greatest Common Factor 1.) List the factors of each number:Factors of 75: 1, 3, 5, 15, 25, 75Factors of 80: 1, 2, 4, 5, 8, 10, 16, 20, 40, 802.) Identify the common factors:The factors that 75 and 80 share are: 1, 53.) Determine the greatest common factor:From the list of common factors, the largest one is 5. Final answer:Therefore, the greatest common factor of 75 and 80 is 5.