## Algebra 1: Common Core (15th Edition)

We have to find the number of combinations of 12 jurors chosen 9 at a time. Use the formula of combination: $_{n}$C$_{r}$=$\frac{n!}{r!(n-r)!}$. Plug in 12 for N and 9 for R: $_{n}$C$_{r}$=$\frac{n!}{r!(n-r)!}$ $_{12}$C$_{9}$=$\frac{12!}{9!(12-9)!}$ -simplify like terms- $_{12}$C$_{9}$=$\frac{12!}{9! (3!)}$ -write using factorial- $_{12}$C$_{9}$=$\frac{12*11*10*9*8*7*6*5*4*3*2*1}{(9*8*7*6*5*4*3*2*1)(3*2*1)}$ -simplify- $_{12}$C$_{9}$=220 220