23, 34, 27, 7, 30, 26, 28, 31, 34 what number is an outlier for the given data? a) 7 b) 23 c) 31 d) 34

The correct answer is 7 , but why is this the answer ? since you asked :) just read below :

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An out-liar is a number that doesn't quite fit in, it should stand out from everything else.
No matter what type of number big or small, in this case the answer is 7.

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Now that we know what the meaning of Out-liar is , you should obviously understand that the number 7 is the only number far away in distance from the rest.

This was my reason being for my answer , I really hope that you find my answer helpful. 
  

3x+9+4x+x=8x+9that's the answer for your question.