Well maybe it is just as @Imrahil says and is just a representation of someone sticking with the wrong answer. However it is not wrong to write 5! = 120 The "!" is a valid mathematical notation, which is equal to the number say "n" multiplied by (n-1) then by (n-2) until you reach 1 It is called Factorial if anyone is interested. Now if we make the equation for 5 factorial (aka. 5!) we get: 5·4·3·2·1 = 120 So just a fancier way of writing 120 Although if I should really nitpick the "x" is technically not the sign for multiplication, and is actually used for "Cross prodcuts". Oh and the division sign is not actually division either or it will at least be phased out for good reason, due to it being potentially misleading and very ugly (if I do say so myself )