Answer: 20.
- A 10
- B 20
- C 30
- D 40
Correct answer: B. 20
Explanation: Liking at least one = 60 + 50 − 30 = 80, so neither = 100 − 80 = 20.
A Venn diagram makes set identities visual: A∪B is everything inside either circle, A∩B is only the overlap, and the region outside both circles represents the complement of their union - directly illustrating De Morgan's law (A∪B)′ = A′∩B′.
Concept context
Types of sets, operations (union/intersection/complement), relations, and types of functions with domain and range