Math Help - Binomial Coefficient proof

1. Binomial Coefficient proof

Hi, I need some help on this problem:

Prove that $\binom {n+1} {k} = \binom {n} {k-1} + \binom {n} {k}$

any help will be appreciated, thanks.

2. You know that $\binom nk=\frac{n!}{(n-k)!k!},$ apply that to the RHS.