Question: If (n + 3)! = 56 [(n + 1)!], find n.
Solution:
(n + 3)! = 56 [(n + 1)!]
$\Rightarrow(n+3) \times(n+2) \times(n+1) !=56[(n+1) !]$
$\Rightarrow(n+3) \times(n+2)=56$
$\Rightarrow(n+3) \times(n+2)=8 \times 7$
$\Rightarrow n+3=8$
$\therefore n=5$
