9! = ?

Answer 1

9x8x7x6x5x4xx2x1 = .
! is just a "factorial" sign, it means to start at that number and multiply each number in a descending order until you get down to x1

Answer 2

by definition,
n! = 1x2x3x...xn

e.g
4! = 1x2x3x4 = 24