The given expression can be simplified as follows:

(n-10)! / 3! (n-3)!

= (n-10)! / 3! * (n-3)(n-4)(n-5)...(2)(1)

= (n-10)(n-9)(n-8)...(3)(2)(1) / (3)(2)(1)

= (n-10)(n-9)(n-8)...(3)

Therefore, the simplified expression is (n-10)(n-9)(n-8)...(3).