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Math Help - I need to find the solution of the system. There are 3 problems.

  1. #1
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    I need to find the solution of the system. There are 3 problems.

    Hello, and thank you for your help. I have been doing this all day, and I cannot get the right answer for the life of me. All other 70 questions I was able to solve. Somehow I am missing it on these. Please show me how you did your work. I do not have to show the work, but I would like to learn and see what I did wrong. God bless.

    1. 0.05X + 0.25Y = 66
    0.15X + 0.05Y = 72

    2. 0.3X - 0.2Y = 4
    0.5X + 0.3Y = 1

    3. 9x-9y = 9
    7y-3x = -5
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  2. #2
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    Quote Originally Posted by OneidaFL View Post
    Hello, and thank you for your help. I have been doing this all day, and I cannot get the right answer for the life of me. All other 70 questions I was able to solve. Somehow I am missing it on these. Please show me how you did your work. I do not have to show the work, but I would like to learn and see what I did wrong. God bless.

    1. 0.05X + 0.25Y = 66
    0.15X + 0.05Y = 72

    2. 0.3X - 0.2Y = 4
    0.5X + 0.3Y = 1

    3. 9x-9y = 9
    7y-3x = -5
    Dear OneidaFL,

    Let us try the first one, 0.05X + 0.25Y = 66\Rightarrow{X=\frac{66-0.25Y}{0.05}}

    Now, 0.15X + 0.05Y = 72

    0.15\left(\frac{66-0.25Y}{0.05}\right)+0.05Y=72

    Simplify and you can get the answer for Y. Then you can find X by substituting Y in one of the two equations. The same method applies for all the other questions as well. Hope you will be able to continue.
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  3. #3
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    Quote Originally Posted by OneidaFL View Post
    1. 0.05X + 0.25Y = 66
    0.15X + 0.05Y = 72
    Multiply by 100 to get rid of decimal points:
    5x + 25y = 6600
    15x + 5y = 7200
    Divide by 5 to simplify:
    x + 5y = 1320 [1]
    3x + y = 1440 [2]

    From [2]: y = 1440 - 3x
    Substitute that in [1]

    OK?

    Others can be solved similarly.
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