5!. i know the answer is 120, nbut what is th ! thanks in advance.

the ! is an operator called "factorial"

5! = 1 x 2 x 3 x 4 x 5

10! = 1 x 2 x 3 x .... x 9 x 10
etc
special case: 0! = 1

so n! is defined for n≥0 , n being a whole number
and is simply the product of consecutive whole numbers from 1 to n