What's the greatest common factor of 45,9,63

The greatest common factor of those numbers is the largest number that you can divide each of those numbers by. Looking at those three numbers, we can see that all three can be divided by 9. We also know that there is now way to divide those numbers evenly by a greater number than 9, because 9 is one of our options, and if we divided 9 by any number greater than 9, we would not get a whole number.