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Math Help - algebra, values pf x and y

  1. #1
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    algebra, values pf x and y

    two questions:
    x over x - 9 = 4 over 7
    x + y over x - y = 5 over 3 .
    that is one question, find x and y, show all steps please...
    the 2nd one.
    x - 3 over 4 = y +2 over 2
    x +y-1 over 6 = x - y + 1 over 5.
    show all steps thanks
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  2. #2
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    Quote Originally Posted by gamecube10074 View Post
    two questions:
    x over x - 9 = 4 over 7
    x + y over x - y = 5 over 3 .
    that is one question, find x and y, show all steps please...
    x/(x - 9) = 4/7
    (x + y)/(x - y) = 5/3

    I'm assuming you're trying to solve this system of equations.

    x = 4/7*(x-9)

    7x = 4*(x - 9)

    7x = 4x - 36

    36 = -3x

    x = -12 -- (1)

    (x + y)/(x - y) = 5/3

    x + y = 5/3*(x - y)

    x + y = 5/3x - 5/3y

    y = (2x)/3 - (5y)/3

    3y = 2x - 5y

    8y = 2x

    y = x/4

    But, from (1), we can substitute x in for y;

    y = (-12)/4

    y = -3

    Thus, we have (-12, -3)
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  3. #3
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    Quote Originally Posted by gamecube10074 View Post
    the 2nd one.
    x - 3 over 4 = y +2 over 2
    x +y-1 over 6 = x - y + 1 over 5.
    show all steps thanks
    (x - 3)/4 = (y + 2)/2

    Multiply both sides by 4;

    x - 3 = 2*(y + 2)

    x - 3 = 2y + 4

    x = 2y + 7 -- (1)

    (x + y - 1)/6 = (x - y + 1)/5

    Multiply both sides by 30;

    5*(x + y - 1) = 6*(x - y +1)

    5x + 5y - 5 = 6x - 6y + 6

    5y = x - 6y + 11

    11y = x + 11

    y = (x + 11)/11

    Substitute:

    y = ([2y + 7] + 11)/11

    11y = 2y + 7 + 11

    11y = 2y + 18

    9y = 18

    y = 2

    And thus,

    x = 2(2) + 7

    x = 11

    The final answer: (11, 2)
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