Answer: 362880
The exclamation mark means factorial notation. The rule is we start with the given number, then count down til we get to 1, multiplying all along the way. In this case, we start with 9, then multiply with 8, 7, 6, etc til we get to 1, like so...
9! = 9*8*7*6*5*4*3*2*1 = 362880
Some calculators have a factorial button built in. The button should be labeled with an exclamation mark.
