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Math Help - Setting up and solving equations to find the price of books

  1. #1
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    Setting up and solving equations to find the price of books

    Hey guys, I am a new poster around here and I really can use a hand here!

    I am in high school and I just cant do this one problem even though I have tried for hours...

    So here's the deal, its a problem with 4 books and I need to find the prices for each one.

    the clues are

    - all the books without the 1st one gives a total of 42$
    - all the books without the 2nd one gives a total of 40$
    - all the books without the 3rd one gives a total of 38$

    and

    - all the books without the 4th one gives a total of 36$

    Thank you for your time!
    Any help or advices would be gladly appreciated!
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  2. #2
    MHF Contributor
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    What have you tried.

    Name the prices.

    A, B, C, and D perhaps.

    B+C+D = 42
    A+C+D = 40

    etc...

    Let's see what you get.
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  3. #3
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    I didnt get no where...
    All that I can conclude was

    A + B + C + D = X

    B + C + D = 42 and X - 42 = A
    A + C + D = 40 and X - 40 = B
    A + B + D = 38 and X - 38 = C
    A + B + C = 36 and X - 36 = D
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  4. #4
    MHF Contributor
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    Why did you introduce 'X'? Get rid of that. It's cute, but it doesn't get you anywhere.

    Have you the ability to solve a well-defined 4x4 system of equations? The coefficients certainly are not challenging.

    Just for the record, X = 52, but the problem statement certainly does not ask for that.
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