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-   -   Can you help me solve this math problem (https://www.askmehelpdesk.com/showthread.php?t=612951)

  • Nov 17, 2011, 08:26 AM
    toneisha
    can you help me solve this math problem
    math x=7y-42x-3y=14
  • Nov 17, 2011, 08:34 AM
    Curlyben
    Seems to have become a little jumbled.
    Would you please clarify your question.
  • Nov 17, 2011, 11:25 AM
    jcaron2
    Quote:

    Originally Posted by toneisha View Post
    math x=7y-42x-3y=14

    I think that's supposed to be two different equations, yes?

    x=7y-42 and
    x-3y=14

    If so, the first equation tells you exactly what x is equal to. You can just substitute that expression in place of the x in the second equation. In other words, wherever you see an x in the second equation, write (7y-42) instead.

    That will give you an equation with only one variable, y, which you should be able to easily solve for. Then you just have to plug that y value back into the first equation to get the value of x.

    If you want to check your answers when you're all done, plug the values you got for x and y into both equations, and make sure they work out to be true. (For the second equation, for example, after you plug in x and y, you should end up with 14 = 14).
  • Nov 18, 2011, 08:15 AM
    Aurora2000
    I am a newbie, and I first apologize if mimeTex is not good.

    If it reads , then see jcaron2's answer.
    If it reads , you have 2 (equivalent) choices:

    1. Substitute in place of , thus you have
    2. is the same as , then the difference between these equations gives you

    In both cases you have a one variable equation. There is no need to check solutions if you do things correctly, and linear equations never gets problems (as sign choices, singularities, etc.).
  • Nov 18, 2011, 11:22 AM
    jcaron2
    I bet your interpretation is correct (the one where the gap is between the 4 and the 2x, not the 42 and the x).

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