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__Find the value of n.__

1. P(n,2)=90 ; 2. P(n,3)=3P(n,2)

I tried like this but I am stuck

1. n! / (n-2)! = 90 and then I don't know ...

2. n!/(n-3!) = 3 n!/(n-2)! ⇔ n! (n-2)! / (n-3)! n! = 3 ⇔ (n-2)! / (n-3)! = 3 here the same

As you can see I'm really stuck with this.