The exclamation mark means "factorial". We start with the given number and count down til we reach 1. We multiply all of the values in the countdown
6! = 6*5*4*3*2*1 = 30*12*2 = 360*2 = 720
3! = 3*2*1 = 6
So because
6! = 720
3! = 6
This means,
(6!)/(3!) = 720/6 = 120
Answer: 120