Compute $\dbinom{8}{2}$.
One way to calculate it is to use the formula $\dbinom{n}{k} = \frac{n!}{k!(n-k)!}$, where $n!$ is the factorial of $n$, which means the product of all positive integers up to $n$. In this case, I can plug in $n=8$ and $k=2$ and simplify: $\dbinom{8}{2} = \frac{8!}{2!(8-2)!} = \frac{8\times 7 \times 6!}{2\times 1 \times 6!} = \frac{8\times 7}{2\times 1} = \frac{56}{2} = 28$. 