The task is to generate the correct answer for a given math problem.
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Question: Problem: a man rows his boat 110 km downstream and 90 km upstream , taking 3 hours each time . find the speed of the stream ?

Answer: 3.5

Question: Problem: if | x - 9 | = 3 x , then x = ?

Answer: - 4.

Question: Problem: a trained covered x km at 30 kmph and another 2 x km at 20 kmph . find the average speed of the train in covering the entire 3 x km .

Answer:
22.5