GCF is the greatest common factor of some numbers
We need to find the GCF of 525, 135, 750
Since all the numbers end by 5 or 0, then
All of them can divide by 5
Then the first common factor of them is 5

Since the sum of digits of 105 = 1 + 0 + 5 = 6, and 6 can divide by 3
Then 3 is a factor of 105
Since The sum of the digits of 27 = 2 + 7 = 9 and 9 can divide by 3
Then 3 is a factor of 27
Since the sum of the digits of 150 = 1 + 5 + 0 = 6 and 6 can divide by 3
Then 3 is a factor of 150
Then 3 is the second common factor of them

Since 35, 9, and 50 can not divide by the same number, then
The greatest common factor of 525, 135, 750 is

The GCF of 525, 135, and 750 is 15