To simply the expression,we should remember an ! in math represents every number (til 1) before that one multiplied or "the product of the integers from 1 to n"
So now that we have the definitions we can simplify by finding the values of each:
(9x8x7x6x5x4x3x2x1)-(4x3x2x1)(5x4x3x2x1)
After simplifying this will equal to 3600