GCF is the greatest common factor of two or more numbers
To find it factorize the numbers and find their common factor, and choose the greatest one
Let us find the factors of 35
35 = 1 * 35
35 = 5 * 7
Then the factors of 35 are 1, 5, 7, 35
Let us find the factors of 25
25 = 1 * 25
25 = 5 * 5
Then the factors of 25 are 1, 5, 25
The common factors of 35 and 25 are 1, 5
The greatest is 5
So the GCF of 35 and 25 is 5