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March 25, 2017

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I need help with this problem
0.3x-0.2y=4
0.5x+0.5y=45/23
3x-2y=40
5x+5y=450/230
6x-47=80
-15x-15y=1350/230
x=5

is this right I need your help.

  • Algebra - ,

    when you multiply 0.5x+0.5y=45/23 by 10 you get
    5x + 5y = 450/23

    (you don't multiply top and bottom by 10, if you did, you wouldn't have changed the right side at all, only the left side.
    And remember, whatever you do to one side, you must do to the other)
    I would then divide 5x + 5y = 450/23 by 5 to get
    x + y = 90/23 , (notice we could have just doubled the original to get the same result)
    now
    3x - 2y = 40, and
    2x + 2y = 180/23
    adding
    5x = 40 + 180/23
    x = 8 + 36/23
    = 220/23
    sub that into x+y= 90/23
    220/23 + y = 90/23
    y = 90/23 - 220/23
    = -130/23

    ( I subbed both of my answers in the original equations and they work!)

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