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Math Help - Solve the Equation

  1. #1
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    Solve the Equation

    Another problem I just crossed. Going to be last for tonight, I need to rest.

    3r-3/r = 7/9 Okay, he is what I've done.

    Divided off the r and got 3-3=7/9
    I multiplied both sides of the equation by the reciprocal 9/7
    Now here's where I'm lost.
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  2. #2
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    Re: Solve the Equation

    Quote Originally Posted by HellBunny View Post
    Another problem I just crossed. Going to be last for tonight, I need to rest.

    3r-3/r = 7/9 Okay, he is what I've done.

    Divided off the r and got 3-3=7/9 ... huh?
    I multiplied both sides of the equation by the reciprocal 9/7
    Now here's where I'm lost.
    is the equation

    \frac{3r-3}{r} = \frac{7}{3}

    or

    3r - \frac{3}{r} = \frac{7}{9}

    ?
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  3. #3
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    Re: Solve the Equation

    Quote Originally Posted by skeeter View Post
    is the equation

    \frac{3r-3}{r} = \frac{7}{3}

    or

    3r - \frac{3}{r} = \frac{7}{9}

    ?
    The first one.
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  4. #4
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    Re: Solve the Equation

    Quote Originally Posted by HellBunny View Post
    The first one.
    \displaystyle \begin{align*} \frac{3r - 3}{r} &= \frac{7}{3} \\ 3(3r - 3) &= 7r \end{align*}

    Now expand the brackets then collect like terms and solve.
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  5. #5
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    Re: Solve the Equation

    I don't have the slightest clue what happened. Why did you change the problem? I know it's still the same, just been rearranged.
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  6. #6
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    Re: Solve the Equation

    Quote Originally Posted by HellBunny View Post
    I don't have the slightest clue what happened. Why did you change the problem? I know it's still the same, just been rearranged.
    Maybe because you need to rearrange it so you can solve it...

    I multiplied both sides by 3 to get rid of the fraction on the right, and multiplied both sides by r to get rid of the fraction on the left.
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  7. #7
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    Re: Solve the Equation

    I tried solving it and still hadn't came out with the right answer.
    I use distributive property 3(3r-3)=7r ; 9r - 9 = 7r ; 9r = 7r + 9 ; I don't get what's next
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  8. #8
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    Re: Solve the Equation

    I made a typo in the previous equation ... the right side should be \frac{7}{9} instead of \frac{7}{3}

    \frac{3r-3}{r} = \frac{7}{9}

    cross multiply ...

    9(3r-3) = 7r

    distribute on the left side ...

    27r - 27 = 7r

    add 27 and subtract 7r from both sides ...

    27r - 7r = 27

    combine like terms on the left side ...

    20r = 27

    divide both sides by 20 ...

    r = \frac{27}{20}

    you're done.
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  9. #9
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    Re: Solve the Equation

    I hate how I can look at a problem after its done and say to myself " I knew how to do that! " but couldn't figure out how to do it. Insane. Thanks you guys.
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