Chapter 3 - Probability - Section 3.4 Additional Topics in Probability and Counting - Exercises - Page 174: 6

True.

$_{n}C_{r}=\frac{n!}{(n-r)!r!}$ $_{7}C_{5}=\frac{7!}{(7-5)!5!}=\frac{7!}{2!\times5!}=\frac{7\times6\times5!}{2!\times5!}=\frac{42}{2}=21$ $_{7}C_{2}=\frac{7!}{(7-2)!2!}=\frac{7!}{5!\times2!}=\frac{7\times6\times5!}{5!\times2!}=\frac{42}{2}=21$ $_{7}C_{5} =~_{7}C_{2}$