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Math Help - Simple fractional equation

  1. #1
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    Smile Simple fractional equation

    So here's the equation.

    Solve:

    7 \frac {1}{2}x  -\frac {1}{2}x = 3 \frac {3}{4} + 39


    I know x = 12 because of the answer key, but I keep getting the wrong answer. I really need a step-by-step explanation.


    thanks
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  2. #2
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    Quote Originally Posted by dreamer09 View Post
    So here's the equation.

    Solve:

    7 \frac {1}{2}x -\frac {1}{2}x = 3 \frac {3}{4} + 39


    I know x = 12 because of the answer key, but I keep getting the wrong answer. I really need a step-by-step explanation.


    thanks
    Hi dreamer09,

    You have terms on the left side of your equation with the variable x in them. Combine these. On the right side, you just have numbers. Combine these.

    7\frac{1}{2}x-\frac{1}{2}x=3 \frac{3}{4}+39

    7x=42 \frac{3}{4}

    Now, if you divide 42 \frac{3}{4} by 7, you will not get 12. You will, in fact, get \frac{171}{28}. Maybe you miscopied the problem. Check it again.
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    Quote Originally Posted by masters View Post
    Hi dreamer09,

    You have terms on the left side of your equation with the variable x in them. Combine these. On the right side, you just have numbers. Combine these.

    7\frac{1}{2}x-\frac{1}{2}x=3 \frac{3}{4}+39

    7x=42 \frac{3}{4}

    Now, if you divide 42 \frac{3}{4} by 7, you will not get 12. You will, in fact, get \frac{171}{28}. Maybe you miscopied the problem. Check it again.
    Oh sorry, yes I left something out.

    7\frac{1}{2}x-\frac{1}{2}x=3 \frac{3}{4}x+39
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  4. #4
    A riddle wrapped in an enigma
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    Quote Originally Posted by dreamer09 View Post
    Oh sorry, yes I left something out.

    7\frac{1}{2}x-\frac{1}{2}x=3 \frac{3}{4}x+39
    Ok, that's better. Combine the tems on the left side first:

    7x=3 \frac{3}{4}x+39

    Next, subtract 3 \frac{3}{4}x from both sides of the equation.

    3 \frac{1}{4}x=39

    Finally divide both sides by 3 \frac{3}{4} to arrive at your desired conclusion.

    Now, if it's the arithmetic that's giving you problems, you might want to convert those mixed fractions to improper fractions. Might make it easier to solve.

    7x=\frac{15}{4}x+39

    Multiply each term by 4.

    28x=15x+156

    Subtract 15x from both sides

    13x=156

    Divide by 13.

    x=12
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