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Math Help - Addition and Subtraction Properties

  1. #1
    Newbie
    Joined
    Sep 2007
    Posts
    8

    Exclamation Addition and Subtraction Properties

    I have this one problem that I need help on, can anyone help me??

    Given: Angle A is comp. to Angle B
    Angle C is comp. to Angle B
    Angle A = (3x + y)
    Angle B = (x + 4y + 2)
    Angle C = (3y - 3)


    Find: Angle B


    Please explain...
    I need some help with this one, I do not understand it...
    HELP!!!
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  2. #2
    Junior Member
    Joined
    Jun 2007
    Posts
    65
    Let's set up a system of Equations:

    We know m\angle A + m\angle B = 90
    and that  m\angle B + m\angle C = 90 which tells us that A and C are congruent.

    Now let's substitute: 3x + y + x + 4y + 2 = 90 and simplify to 4x + 5y = 88
    And for our second equation x + 4y + 2 + 3y - 3 = 90 and simplify this to x + 7y = 91

    Now to get x by itself  x = 91 - 7y and let's plug it into the first equation  4(91 - 7y) + 5y = 88 simplify  364 - 28y + 5y = 88 and now we get  -23y = -276 and  y = 12

    Now just put y into the original equation  4x + 5(12) = 88 and get  4x = 28, x = 7 . So now we have  y = 12, x = 7

    Put the values back into the original problems to see if they are true and you are done.
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