let's say i have a hand of cards.

the number of cards i have in my hand is x > 3.

how many unordered different triples of cards can i form with the cards in my hand?

example:
i have the following cards in my hand: A B C D
i could form 

A B C

A B D

A C D

B C D

4 different triples can be formed.

i am looking for a formular that gives me the number of triples depending on x.