SOLUTION: A math professor tells me that the problem: "the difference of 9 and 3 times a number is 69 is written -9 + 3x = 69" I agree but on another site it states it is 9 - 3x = 69? If I r

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Question 918816: A math professor tells me that the problem: "the difference of 9 and 3 times a number is 69 is written -9 + 3x = 69" I agree but on another site it states it is 9 - 3x = 69? If I read the math words correctly difference is subtraction thus -9, and means addition, which makes sense with what the professor stated instead of what I saw on another site. Which is correct?
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Ambiguity is a problem. Either equation can be good. The professor should express the description without ambiguity, but did not.

"the difference of 9 and 3 times a number..."
Put into symbolism is this:
abs%289-3x%29


Analyze the whole question further.
highlight_green%28abs%289-3x%29=69%29. THAT is what should be formed, based on the worded description.

If you want to solve that for x, you could first simplify, dividing left and right members by 3:

%281%2F3%29abs%289-3x%29=69
abs%283-x%29=23
And from that, you have the two different cases,
highlight%283-x=23%29 red%28OR%29 highlight%28-%283-x%29=23%29

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

A math professor tells me that the problem: "the difference of 9 and 3 times a number is 69 is written -9 + 3x = 69" I agree but on another site it states it is 9 - 3x = 69? If I read the math words correctly difference is subtraction thus -9, and means addition, which makes sense with what the professor stated instead of what I saw on another site. Which is correct? 


If 3 times the number (3x) is LARGER than 9, then - 9 + 3x = 69, or 3x - 9 = 69 is CORRECT. 

However, if 9 is the larger of the 2, then 9 - 3x = 69 is CORRECT.



On the other hand, in a case such as this: when the larger of the 2 (9 or 3x) is not specified, it's usually the

norm to write the equation/expression the way it was given. It was given as the difference between 9 and 3x = 69,

so I would write it as such (9 - 3x = 69).