Answer:
[tex]\displaystyle ^{22}C_{20} =231[/tex]
[tex]\displaystyle ^{12}C_{8} =495[/tex]
Step-by-step explanation:
Binomial Coefficients
[tex]\displaystyle \binom{n}{r} \: = \:^{n}C_{r} = \frac{n!}{(n-r)! \, r!}[/tex]
[tex]\begin{aligned}\displaystyle \implies ^{22}C_{20} & = \frac{22!}{(22-20)! \, 20!}\\\\ & =\frac{22!}{2! \, 20!}\\\\ & =\frac{22 \cdot 21 \cdot 20!}{2! \, 20!}\\\\ & =\frac{22 \cdot 21}{2 \cdot 1}\\\\ & =\frac{462}{2}\\\\ & =231\end{ailgned}[/tex]
[tex]\displaystyle \begin{aligned} \implies ^{12}C_{8} & = \frac{12!}{(12-8)! \, 8!}\\\\ & =\frac{12!}{4! \, 8!}\\\\ & =\frac{12 \cdot 11 \cdot 10 \cdot 9 \cdot 8!}{4! \, 8!}\\\\ & =\frac{12 \cdot 11 \cdot 10 \cdot 9}{4 \cdot 3 \cdot 2 \cdot 1}\\\\ & =\frac{11880}{24}\\\\ & =495\end{aligned}[/tex]
