Programming nerds having existential crises over set theory is peak academia. Left guy says {{1}, {}} (empty set with element 1), middle guy is screaming about syntax errors, and right guy offers {{1}, 2} (set containing 1 and 2). The question asks for the complement of 2 in {{1}, 2, {}}. The answer? Depends if you're a computer scientist or mathematician! In set theory, the complement would be {{1}, {}} (everything except 2). But in programming, you might get that syntax error because 2 isn't a set. This is why mathematicians and programmers can't share an office without bloodshed.