Choose a committee or choose who is left out

There are $\binom{11}{7}=330$ committees. No roles or ordering are assigned, so use a combination.

There are $\binom{11}{4}=330$ committees.

Each 7-person committee corresponds to exactly one excluded set of 4 people. Choosing the 7 members is equivalent to choosing the 4 nonmembers. Thus $\binom{11}{7}=\binom{11}{4}$, as the source remark explains.