Answer
$36$
Work Step by Step
Binomial coefficient can be found as:
$\dbinom{n}{r}=\dfrac{n!}{r!(n-r)!}$
Thus, $\dbinom{9}{2}=\dfrac{9!}{2!(9-2)!}$
or, $=\dfrac{ 9 \cdot 8 \cdot 7!}{2!(7)!}$
or, $=\dfrac{ 9 \cdot 8 \cdot 7!}{2 \cdot 1(7)!}$
or, $=36$
