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Math Help - Order of Operations Problem

  1. #1
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    Order of Operations Problem

    This is really bugging me. Up until these last few problems in the textbook, O of O was pretty easy for me. So I figure the thing I'm not getting can't be too tough. But class was cancelled today and I want to get this solved so I can get on with things. Anyway, here it is:

    4{[5 (x-3) +2] -3[2(x+5)-9]}

    The answer according to the textbook is -4x -64 but I'm not coming up with it.

    Any help is greatly appreciated. Thanks!
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  2. #2
    A Plied Mathematician
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    You want to work from the inside out. What would be a first step?
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  3. #3
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    Hi, and thank you very much for taking the time. My first step would be to use the distributive properties and multiply both x and -3 by 5.

    4{[5(x -3) +2]

    This leaves you with 4[5x -15 +2].

    Then add like terms within the brackets and you have 4[5x -13].

    Now at this point, I'm not sure what to do because while this problem is in the textbook there's no example for it. Or maybe due to the brackets and squiggly line thingies (sorry, their name escapes me right now) I'm performing something out of order.

    Anyway, distributing the 4 I come up with 20x -52.


    For the right side: -3[2(x +5) -9]}

    Multiply both x and +5 by 2 for -3[2x +10 -9]

    Add like terms inside the brackets to get -3[2x+1].

    Now it seems like you should distribute the the -3 to come up with -6x -3

    Combine the like terms for a final answer of -14x -55

    But that's not the answer. Thank you again for helping me in anyway.
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  4. #4
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    you are distributing the 4 too soon ...

    4{[5 (x-3) +2] -3[2(x+5)-9]}

    4{[5x-13] - 3[2x+1]}

    4{[5x-13] - 6x - 3}

    4{-x - 16}

    -4x - 64
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  5. #5
    A Plied Mathematician
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    Your 4 on the extreme left side of the equation has to multiply everything. You're not letting it multiply your right side expression. I would fix that first.
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  6. #6
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    Yes! I knew it was a simple fix. Thank you very much for putting a smile on my face.

    What a great site. Hopefully at some point in the future I'll be able to contribute to it.

    Thanks again.
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