Question: what is the greatest common factor in 7 and 35?
Answer: The factors of 7 are 7, 1. The factors of 35 are 35, 7, 5, 1. The common factors of 7 and 35 are 7, 1, intersecting the two sets above. In the intersection factors of 7 ∩ factors of 35 the greatest element is 7. Therefore, the greatest common factor of 7 and 35 is 7.