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Math Help - Please help it's been too long since I took algebra, I've been stuck on this problem

  1. #1
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    Please help it's been too long since I took algebra, I've been stuck on this problem

    Six times the quantity of 4 minus a number is 15. Find the number. Show your work. This should be easy to pros. Thanks
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  2. #2
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    Re: Please help it's been too long since I took algebra, I've been stuck on this prob

    Model the problem like this:
    x is the quantity needed
    x - 4 the quantity minus 4
    six time the quantity minus 4 is: ______________fill the blank
    the last one is = 15.
    Find the quantity.

    Does this help
    Thanks from topsquark
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  3. #3
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    Re: Please help it's been too long since I took algebra, I've been stuck on this prob

    Use symbols for the words.

    \begin{matrix}\mbox{Six} & \mbox{times} & \mbox{the quantity of} & 4 & \mbox{minus} & \mbox{a number} & \mbox{is} & 15 \\ 6 & \times & ( & 4 & - & x & )= & 15\end{matrix}

    So, solve for x
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    Re: Please help it's been too long since I took algebra, I've been stuck on this prob

    Ok thanks but I need to see the whole problem to understand it...I'm not getting the same answer that's in the back of the book which is 1.
    I multiplied 6 times 4 and got 24 then 6 times x which is 6x...I added 24 to both sides and got 15 + 24 which is 39 on the right and divided that by 6 and MY answer was 6 and 1/2 but the answer is 1.5. What did I do wrong...HELP! thanks
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    Re: Please help it's been too long since I took algebra, I've been stuck on this prob

    \begin{align*}6(4-x) & = & 15 \\ 24 - 6x & = & 15 \\ -24 & & -24 \\ \hline -6x & = & 15-24 \\ -6x & = & -9 \\ \times -\tfrac{1}{6} & & \times -\tfrac{1}{6} \\ \hline x & = & \dfrac{9}{6} \\ x & = & \dfrac{3}{2}\end{align*}
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    Re: Please help it's been too long since I took algebra, I've been stuck on this prob

    See I multiplied 24 by both sides I get confused as to how do I know I'm not supposed to do that.
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    Re: Please help it's been too long since I took algebra, I've been stuck on this prob

    You had 24-6x = 15. If you add 24 to both sides, you get (24 - 6x) + 24 = 15 + 24. Add this up, and now you have 48 - 6x = 39. You are trying to get all terms with an x on one side and all numbers on the other. So, adding 24 to both sides did not help at all. So, you try subtracting 24 from both sides. 24 - 6x - 24 = 15 - 24. Since 24-24 = 0, on the left hand side, you are only left with -6x. On the right hand side, 15-24 = -9.
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    Re: Please help it's been too long since I took algebra, I've been stuck on this prob

    Thank you...
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    Re: Please help it's been too long since I took algebra, I've been stuck on this prob

    Quote Originally Posted by Tlcmel View Post
    See I multiplied 24 by both sides I get confused as to how do I know I'm not supposed to do that.
    Please help it's been too long since I took algebra, I've been stuck on this problem-untitled2.gif
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