i dont have any idea what is this

[frigid compass]

I was preparing to my math exam and i saw this(in brackets), i dont have any idea what is this thing. Id like to receive answer as soon as possible!

[forest hare]

@frigid compass it's notation to express n choose r

specifically

$$C(n,r) = \binom{n}{r} = \frac{n!}{( r! (n - r)! )}$$

[deft wave]

Kaiser

[forest hare]

this represents the number of ways you can choose r items from a set of n items

[frigid compass]

Thx you very much

[amber root]

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