The exclamation mark at the end of any number indicates a factorial. You may be able to find this button in your calculator, though where it is varies.
A factorial is the product of the integer and all of the integers below it (greater than 0).
So, 9 factorial = 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1
6 factorial = 6 x 5 x 4 x 3 x 2 x 1
We can immediately eliminate the numbers that are the same on the top and bottom, since this is a fraction. That leaves us with the following multiplication problem to solve.
9 x 8 x 7 = 504
Hope this helps!