SOLUTION: And this one I'm really confused about. I gor the answer Fred is 14yo but it tells me the answer is wrong. Fred is 3 years older than his sister Mary. In 7 years she will be six-s

Algebra ->  Customizable Word Problem Solvers  -> Age -> SOLUTION: And this one I'm really confused about. I gor the answer Fred is 14yo but it tells me the answer is wrong. Fred is 3 years older than his sister Mary. In 7 years she will be six-s      Log On

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Question 512388: And this one I'm really confused about. I gor the answer Fred is 14yo but it tells me the answer is wrong.
Fred is 3 years older than his sister Mary. In 7 years she will be six-sevenths of his age. How old is Fred?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Fred is 3 years older than his sister Mary. In 7 years she will be six-sevenths of his age. How old is Fred?
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Equations:
f = m + 3
(m+7) = (6/7)(f+7)
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Substitute for "m" and solve for "f":
f-3+7 = (6/7)(f+7)
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7(f+4) = 6(f+7)
7f + 28 = 6f + 42
f = 14 yrs (Fred's age now)
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Note: You are correct.
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Cheers,
Stan H.