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Math Help - Algebra - solve for x and y

  1. #1
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    Algebra - solve for x and y

    I have two equations:

    18x + 3y = 120
    x + y = 15

    I know that the answers are:

    x = 5
    y = 10

    I could only solve it by punching in numbers and seeing if the problem was solved. I would like to know HOW to come about with the answer using Algebra.

    Thanks...
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  2. #2
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    Quote Originally Posted by gilmoujr
    I have two equations:

    18x + 3y = 120
    x + y = 15
    Are you familiar with substitution? In the second equation, can you solve for one variable to plug into the first equation?
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  3. #3
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    Sigh. Ok, I'll get you started.

    y=15-x. Now, make that substitution into your first equation and the answer should be apparent.
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  4. #4
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    My humblest apologies. I actually remembered how to do it shortly after posting the question. When I came back (after explaining to my daughter how to do it), you had already responded. I appreciate the assistance that you provide (and this forum). I am going to bookmark it for my daughter's (and mine for that matter) reference. I searched the internet for over an hour before getting a hit to your site.

    Again, thank you very much for the excellent forum.
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  5. #5
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    Oh, sorry. I didn't mean to be disrespectful, it's just many people want a simple answer and don't care how it's done. I'm glad you are not one of those people .

    Jameson
    Last edited by Jameson; November 8th 2005 at 06:54 PM.
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