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25 March, 19:15

If 3x+2y=12 and - 4x+6y=24 what is the value of - x+2y

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  1. 25 March, 19:22
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    (1) 3x+2y=12

    (2) - 4x+6y=24

    Solving the system of equations using the method of substitution:

    Isolating y in the first equation:

    (1) 3x+2y=12→3x+2y-3x=12-3x→2y=12-3x→2y/2 = (12-3x) / 2→y = (12-3x) / 2

    Replacing "y" by (12-3x) / 2 in the second equation:

    (2) - 4x+6y=24

    y = (12-3x) / 2→-4x+6[ (12-3x) / 2]=24

    Solving for x:

    -4x+3 (12-3x) = 24

    -4x+36-9x=24

    -13x+36=24

    -13x+36-36=24-36

    -13x=-12

    -13x / (-13) = - 12 / (-13)

    x=12/13

    Replacing "x" by 12/13 in y = (12-3x) / 2

    x=12/13→y=[12-3 (12/13) ]/2

    y = (12-36/13) / 2

    y={[ (13) (12) - 36]/13}/2

    y=[ (156-36) / 13]/2

    y = (120/13) / 2

    y = (120/13) (1/2)

    y=60/13

    x=12/13; y=60/13

    -x+2y=-12/13+2 (60/13)

    -x+2y=-12/13+120/13

    -x+2y = (-12+120) / 13

    -x+2y=108/13

    Answer: The value of - x+2y is 108/13
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