Answer
$1$
Work Step by Step
We know that $C(n,r)=\dfrac{n!}{(n-r)!r!}$, $0!=1$, and $C(n,0)=1$.
Hence,
$C(15,15)=\dfrac{15!}{(15-15)!\cdot15!}=\dfrac{15!}{0!\cdot15!}=1$
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