Verified Answer :

soshahril

  1. x + y = 5 ⇒ x = 5 - y 
    2(5 - y) - y = 7 (substitute)
    10 - 2y - y = 7 (distribute)
    10 - 3y = 7 
    -3y = -3 (subtraction)
    y = 1(divide)

    x + (1) = 5 (substitute then solve)
    x = 4

    2.
    –4x – 6(–2x + 6) = 4 (substitute)
    –4x + 12x – 36 = 4  (solve)
    8x –36 = 4
    8x = 40
    x = 5

    y = –2(5) + 6
    y = –10 + 6
    y = –4

    3.
    3x + y = 7     ⇒ y = 7 - 3x
    -7x - 5(7 - 3x) = 25
    -7x - 35 + 15x = 25
    8x - 35 = 25
    8x = 60
    x = 7.5

    y = 7 - 3(7.5)
    y = 7 - 22.5
    y = 15.5

    4.
    x + 3y = 9     ⇒ x = 9 - 3y
    2(9 - 3y) + 4y = 7
    18 - 6y + 4y = 7
    - 2y + 18 = 7
    - 2y = -11
    y = 5.5

    x = 9 - 3(5.5)
    x = 9 - 16.5
    x = - 7.5

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