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16. What number should replace the question mark?
  IQ test. Fast and free online iq test # 3 with answers and solutions. Question # 16. What number should replace the question mark?
 

Explanation:
The number in the center = lower left number × lower right number + upper left number ÷ upper right number. (5 × 3 + 42 ÷ 14 = 18).