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using the substitution method what is the answer to this problem, x+3y=7 x+4y=12

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    x + 3 y = 7 Subtract 3 y to both sides

    x + 3 y - 3 y = 7 - 3 y

    x = 7 - 3 y

    Put x = 7 - 3 y into equation x + 4 y = 12

    7 - 3 y + 4 y = 12

    7 + y = 12 Subtract 7 to both sides

    7 + y - 7 = 12 - 7

    y = 5


    Replacing y = 5 into x = 7 - 3 y gives

    x = 7 - 3 * 5

    x = 7 - 15

    x = - 8

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