In a party with 100 people, among any set of four there is at least one person who knows each of the other three. There are three people who are not mutually acquainted with each other(that is none of the three knows any of the other two). Prove that the other 97 people know everyone at the party. (Assume that if A knows B, then B also knows A.)

I'm not sure I even understand the question, so I'm having trouble even getting started