The greatest common factor of two numbers is equal to the product of common factors of both the numbers.

factors of 28 = 2 x 2 x 7

factors of 75 = 3 x 5 x 5

Common factors of 28 and 75 = 0

So, there is no greatest common factor of 28 and 75.

factors of 28 = 2 x 2 x 7

factors of 75 = 3 x 5 x 5

Common factors of 28 and 75 = 0

So, there is no greatest common factor of 28 and 75.