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20. What number should replace the question mark?
  IQ test. Accurate and free online iq test # 3 with answers and solutions. Question # 20. What number should replace the question mark?
 

Explanation:
In the first line: -2, -4, -8. In the second line: -3, -9, -27. In the third line: -4, -16, -64.
(94 - 4 = 90; 90 - 16 = 74; 74 - 64 = 10).