Factor out the gcf. use the distributive property to write an equivalent expression for 9d-18f

The GCF of 9d and - 18f is the value 9

This is because 9 is the largest factor that goes into 9d and - 18f

We can factor each part like so

9d = 9*d

-18f = 9 * (-2f)

allowing us to say ...

9d - 18f = 9*d + 9 * (-2f)

9d - 18f = 9 (d-2f)

If we use the distributive property to distribute the 9 through to (d-2f), we end up with 9d-18f again. This is a good way to check the answer

Answer: 9 (d-2f)