## Thinking Mathematically (6th Edition)

The number of possible combinations if r items are taken from n items is nCr = $\frac{n!}{r!(n-r)!}$ 8C7 = $\frac{8!}{7!(8-7)!}$ =$\frac{8!}{7!}$ =$\frac{8*7!}{7!}$ Since 7! is both in the numerator and the denominator, we cancel it out, leaving us with 8.