Hey any help with the following would be much appreciated:

Solve for n where:

P (n,5)=42 * P (n,3)

based on the fact C(n,r)=n!/(n-r)r! , I got:

n!/(n-5)!5!=42* n!/(n-3)!3!

, is this the right step to start? if not, why not? and what would be the proper solution to this problem???