Question 1109900
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You have to be a bit careful with this....<br>
In everyday usage, the difference between two numbers is always thought of as being a positive number.  So the difference of 8 and 3 is 5, and the difference of 3 and 8 is 5.<br>
That is (I assume) why the other tutor used absolute value symbols in her equation.<br>
But often in mathematics, the context tells you that "the difference of a and b" means ONLY a-b, and not the other way around.  So the difference of 8 and 3 would still be 5 (8-3=5); but the difference of 3 and 8 would be -5 (3-8 = -5).<br>
In your question, there is no context to help us decide whether or not the answer has to be positive.  Therefore, I would suggest a better translation of the given statement is<br>
2(x-9) = 7<br>
rather than<br>
2|x-9| = 7