42x^6y^8 = 2 * 3 * 7 * x * x * x * x * x * x * y * y * y * y * y * y * y * y
30x^2y^6 = 2 * 3 * 5 * x * x * y * y * y * y * y * y
30x^4y^3 = 2 * 3 * 5 * x * x * x * x * y * y * y
The GCF is made of the factors that appear in both 42x^6y^8, 30x^2y^6, and 30x^4y^3. In this case that's 2 * 3 * x * x * y * y * y = 6x^2y^3
Answer: The GCF of 42x^6y^8, 30x^2y^6, and 30x^4y^3 is 6x^2y^3.