You can
put this solution on YOUR website!If I want P1(4 cards same suit), I don't care what
the 1st card is, so I'll call P1(1st card) =

,
which means I'm certain to get any one of the cards.
Now I have that card, and it is a certain suit, say
clubs. There are 12 clubs left, so my chances of getting
another club is

Now there are 11 clubs left

, and

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There are 13 groups of 4 cards which are the same rank
I don't care what the 1st card is

I've got the 1st card. Say it is a 9

is P2(another 9)

is P3(another 9)

is P4(another 9)

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given:

Multiply right side by