Of those three, who is the oldest?
SELECT T3.Name FROM debate_people AS T1 JOIN debate AS T2 ON T1.Debate_ID   =   T2.Debate_ID JOIN people AS T3 ON T1.Affirmative   =   T3.People_ID WHERE T2.Num_of_Audience  >  200 order by T3.age desc limit 1
oldest refers to MAX(age); those three refers to a subset of people, presumably defined by another condition such as participation in a debate with more than 200 audience members;