SOLUTION: The difference of two numbers is 7. The second is 7 less than 2 times the first. What are the two numbers?

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Question 111467: The difference of two numbers is 7. The second is 7 less than 2 times the first. What are the two numbers?
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!
You need to first express the problem symbolically. First thing you need are symbols for the two numbers, so let's call them n%5B1%5D and n%5B2%5D.
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The first fact we know is that the difference of these two numbers is 7. So, let's call n%5B2%5D the larger of the two numbers, so we can write n%5B2%5D-n%5B1%5D=7
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Our next fact says "The second is 7 less than 2 times the first." So let's write:
n%5B2%5D=2n%5B1%5D-7
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Since the second equation gives us an expression for n%5B2%5D directly, let's just substitute into the first equation:
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2n%5B1%5D-7-n%5B1%5D=7
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Add 7 to both sides and collect terms to get:
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n%5B1%5D=14
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Now put this value back into equation 1:
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n%5B2%5D-14=7, so
n%5B2%5D=21
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Last step, check your answer.
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21-14=7, and
21=2%2814%29-7. Since both of those statements are true, the answer checks.