The greatest common factor of a number is the largest factor shared between the numbers you're looking at, otherwise known as common. So the factors of 12 are 1, 2, 3, 4, 6, and 12; the factors of 15 are 1, 3, 5, 15; and the factors of 22 are 1, 2, 11, 22. The only common factor here is 1, and is thus the GCF of your three numbers.
The GCF of 12 15 and 22 is 1.
The GCF is 3.
The GCF is 3.
The GCF of 12 and 15 is 1
The GCF is 1.
The GCF is 3.
GCF(12, 15, 18) = 3
GCF(15, 12, 45) = 3
The GCF of 9, 12, 15 is 3.
The GCF is 15.
The GCF is: 1
The GCF is 1.