Solve for n where....

b) P (n,5) = 42 x P(,3) -- out of 5 marks

I know that you have to split up the equation into two sides (left side = right side)

This is as far as I've come with the question..

LS = n! divided by (n-5) RS = 42 x n! divided by 2!

please help me with the rest of the steps!

Thanks in advance