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Math Help - Equation help

  1. #1
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    Equation help

    1/3 - x+1/5 = x/3

    15(1/3-x/5+1/5) = 15(x/3)

    15/3-15x/5+15/5 = 15x/3

    5-3x+3=5x

    8-3x=5x

    8/8=8x/8

    x=1


    The book gets 1/4

    have I made a mistep, Ive done this problem 3 times?
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  2. #2
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    Quote Originally Posted by Aristoxenus View Post
    1/3 - x+1/5 = x/3
    Here is the first mistake: You didn't use brackets! Actually you mean:

    1/3 - (x+1)/5 = x/3

    Better learn some LaTeX.

    15(1/3-x/5+1/5) = 15(x/3)

    15/3-15x/5+15/5 = 15x/3

    5-3x+3=5x

    8-3x=5x

    8/8=8x/8

    x=1


    The book gets 1/4

    have I made a mistep, Ive done this problem 3 times?
    To multiply through by 15 is the right idea:

    \dfrac13-\dfrac{x+1}5 = \dfrac x3~\buildrel\cdot \rem 15 \over \implies ~  5-3(x+1)=5x

    Expand the bracket, collect like terms - and you'll get the given result.
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  3. #3
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    Thank you
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