To find the Greatest Common Factor (GCF) of 90 and 252, we can begin by listing the factors of each number:
Factors of 90: 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90
Factors of 252: 1, 2, 3, 4, 6, 7, 9, 12, 14, 18, 21, 28, 36, 42, 63, 84, 126, 252
From these lists, we can see that the common factors of 90 and 252 are: 1, 2, 3, 6, 9, 18.
Therefore, the GCF of 90 and 252 is 18.