To find the greatest common factor (GCF) of 42 and 66 and express it as a factor, you can first determine the prime factors of each number.
Prime factors of 42:
42 = 2 * 3 * 7
Prime factors of 66:
66 = 2 * 3 * 11
Now, identify the common prime factors between 42 and 66. These are 2 and 3.
So, the GCF of 42 and 66 is 2 * 3, which is 6.
Therefore, you can express the GCF as a factor: 6 is a factor of both 42 and 66.