SOLUTION: Twice the difference of a number and 9 is 7. Translate the sentence into an equation.

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Question 1109900: Twice the difference of a number and 9 is 7.
Translate the sentence into an equation.

Found 2 solutions by josgarithmetic, greenestamps:
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
2%2Aabs%28n-9%29=7
OR
2%2Aabs%289-n%29=7

-
If you knew or were given that n%3E9, then 2%28n-9%29=7.

Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


You have to be a bit careful with this....

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.

That is (I assume) why the other tutor used absolute value symbols in her equation.

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).

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

2(x-9) = 7

rather than

2|x-9| = 7