Hi everyone, long time reader, but I just signed up.

I am trying to work out some problems but I cannot figure out how to go about it.

1) Dice Rolling

After working out part of the problem, I learned that of 2 dice, I have a 13/36 chance of rolling numbers that equal 2,5,9, or 10...

I am now trying to figure out in 4 rolls, what are the chances I only get 2,5,9, or 10 once? In 4 rolls, I have 36^4 chances I believe... No idea where to go from here.

2) 10 people going into hotel rooms. Between the 10 people, they have (1) three person room, (2) two person rooms, and (3) one person rooms.

After trying to read my very incomprehensible book, I came up that I needed to do the following... (10!/(6!4!)) -> Is this correct?