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Math Help - Help !

  1. #1
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    Help !

    Hello,

    I am trying to solve this equation:
    7x + 3y = 12
    3x + 7y = 6

    If x and y satisfy the system of equations above, what is the value of x-y?

    I have tried really hard to solve this, I am appalling bad at Math ! Any help would be appreciated..
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: Help !

    Using elimination, we could multiply the first equation by 3 and the second by -7 to get:

    21x+9y=36

    -21x-49y=-42

    Now, add the equations to eliminate x, and then solve for y. Then plug in this value for y into either original equation to find x.

    What do you find?
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  3. #3
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    Re: Help !

    easy way to find x-y in this question is just subtract 2nd equation from 1st and then divide the whole by 4
    7x-3x+3y-7y=12-6
    4x-4y=6
    x-y=6/4
    x-y=3/2
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  4. #4
    MHF Contributor MarkFL's Avatar
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    Re: Help !

    LOL, I misread the question, I thought the OP was wanting to find (x,y), not x - y.
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  5. #5
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    Re: Help !

    Thanks guys !
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