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| Math Central | Quandaries & Queries |
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Subject: equations with variables on both sides How do you write an equation for this: The difference when 7 less than a number is subtracted from twice the number is 12. And also, what is the number? |
Hi,
You are looking for a number that I am going to call n. Now look at the sentence
The difference when 7 less than a number is subtracted from twice the number is 12.
7 less than the number is n - 7 so I can rewrite the sentence
The difference when n - 7 is subtracted from twice the number is 12.
Twice the number is 2n thus
The difference when n - 7 is subtracted from 2n is 12.
n - 7 is subtracted from 2n is 2n - (n - 7) so
The difference 2n - (n - 7) is 12.
Hence the equation to solve is
2n - (n - 7) = 12
Penny
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