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Math Help - Pre algebra problem

  1. #1
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    Pre algebra problem

    Mrs jones gives $680 each year to charity. She gives the united way twice as much as the Red Cross but only half as much as the American heart association. How much does she give to the American heart association? I get to 2x+x+1/2x=680. But I get confused because of the 1/2 so I have no idea how to solve it.
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  2. #2
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    Re: Pre algebra problem

    Hey Th03.

    Can you collect all the x terms to get an equation ax=b for real numbers a and b? (Also consider multiplying both sides by 2 to get rid of the fractions).
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  3. #3
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    Re: Pre algebra problem

    3x+1/2x=180. I just don't know what to do with the 1/2. It confuses me. If it was a whole number I could finish it. But you say multiply the side by two to get rid of a fraction. Why am I able to do that? It just doesn't make sense why I can do that. Thanks for the help
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  4. #4
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    Re: Pre algebra problem

    Multiplying both sides by a constant will preserve the equality. With regards to the half, 3x + 1/2x = 3.5x = 180 so x = 180/3.5
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  5. #5
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    Re: Pre algebra problem

    Oh I see what you mean. I multiplied all sides by 2 and got the same answer as 680/3.5x. Thank you for the help
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