## Geometry: Common Core (15th Edition)

This is given by $_{10}C_3$ We know that: $_nC_r =\frac{_nP_r}{r!} = \frac{n!}{(n-r)!r!}$ $_{10}C_3 = \frac{10!}{(10-3)!3!}$ We also know that: $x! = x(x-1)(x-2)...(1)$ Thus, we have: 120