Factorial is the repetition multiplication of the values of a number. 

The symbol is the same with the exclamation sign in English Language. 

For example: 

      5! = 5 x 4 x 3 x 2 x 1 = 120

      6! = 6 x 4 x 3 x 2 x 1 = 720 

 It is important to note that the expansion of a number in factorial must get to one at this level.

Then, the procedure is valid. 

      Example : Find the value of 3 factorial plus 4 factorial. 

                This means: 

                              3! + 4! 

                              3! = 3 x 2 x 1 = 6

                              4! = 4 x 3 x 2 x 1 = 24

                     Then =  6 + 24 = 30