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11. Select the image you want to add instead of the question mark.
  IQ test. Fast and free online iq test # 3 with answers and solutions. Question # 11. Select the image you want to add instead of the question mark.
 

Explanation:
Add the contents of the first two boxes to obtain the contents of the third box, except when two lines or symbols appear in the same position in the first two boxes, in which case they are cancelled out.