Answer:The common factor of 3, 6, and 9 is 3. Step-by-step explanation:Factors of 3: 1, 3Factors of 6: 1, 2, 3, 6Factors of 9: 1, 3, 9The largest number that appears in all three lists is 3. Therefore, the greatest common factor (GCF) of 3, 6, and 9 is 3.