Answer:
6
Step-by-step explanation:
We can obtain the greatest common factor by listing the factors of the 2 numbers, that is
Factors of 18 are 1, 2, 3, 6, 9, 18
Factors of 42 are 1, 2, 3, 6, 7, 14, 21, 42
The common factors are 1, 2, 3, 6
The greatest common factor is 6
