I have to find the number of elements $n$ so that when their number is increased by $2$, the number of their permutations $m$ increases $56$ times. Can I write it down with the following equation?
$(n+2)! = 56m$
If so, how can I simplify it to compute the number of elements n?
$(n + 2)! = 56 n!$
$(n + 2) (n + 1) n! = 56 n!$
$(n + 2) (n + 1) = 56$
Solving for $n \in \mathbb{N}$ yields $\boxed{n = 6}$.