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I know the correct answer is x=-32/19 because my teacher gives us the answers on the back of our worksheet, but when I do the actual work I get x=3

It's so simple, yet I've tried several times and get the same answer. Could anyone explain how to do it?

3/4x-2/3x-4=1/6x-7

 Sep 2, 2014

Best Answer 

 #2
avatar+128599 
+5

So, I assume we have

(3/4)x - (2/3)x - 4 = (1/6)x - 7      ???

Mutiply through by the LCD of 3,4 and 6 =12...this gives us

9x - 8x - 48 = 2x - 84  simplify

x - 48 = 2x -  84       subtract x from both sides and add 84 to both sides

36 = x

 

 Sep 2, 2014
 #1
avatar+169 
+5

$${\frac{{\mathtt{3}}}{{\mathtt{4}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\frac{{\mathtt{2}}}{{\mathtt{3}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{4}} = {\frac{{\mathtt{1}}}{{\mathtt{6}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{7}}$$

 

$${\frac{{\mathtt{3}}}{{\mathtt{4}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\frac{{\mathtt{2}}}{{\mathtt{3}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\frac{{\mathtt{1}}}{{\mathtt{6}}}}{\mathtt{\,\times\,}}{\mathtt{x}} = {\mathtt{4}}{\mathtt{\,-\,}}{\mathtt{7}}$$

 

$${\frac{{\mathtt{9}}}{{\mathtt{12}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\frac{{\mathtt{8}}}{{\mathtt{12}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\frac{{\mathtt{2}}}{{\mathtt{12}}}}{\mathtt{\,\times\,}}{\mathtt{x}} = -{\mathtt{3}}$$

 

$${\frac{\left({\mathtt{9}}{\mathtt{\,-\,}}{\mathtt{8}}{\mathtt{\,-\,}}{\mathtt{2}}\right)}{{\mathtt{12}}}}{\mathtt{\,\times\,}}{\mathtt{x}} = -{\mathtt{3}}$$

 

$${\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{12}}}}{\mathtt{\,\times\,}}{\mathtt{x}}\right) = -{\mathtt{3}}$$

 

$${\mathtt{x}} = {\mathtt{\,-\,}}{\frac{{\mathtt{3}}}{{\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{12}}}}\right)}}$$

 

$${\mathtt{x}} = {\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{12}} = {\mathtt{36}}$$

 

You probably gave a wrong equation or the wrong answer, 19 is a prime number and doesn't appear anywhere in the original equation (neither does a multiple of 19). This makes it highy unlikely that a fraction including 19 would be the answer.

 Sep 2, 2014
 #2
avatar+128599 
+5
Best Answer

So, I assume we have

(3/4)x - (2/3)x - 4 = (1/6)x - 7      ???

Mutiply through by the LCD of 3,4 and 6 =12...this gives us

9x - 8x - 48 = 2x - 84  simplify

x - 48 = 2x -  84       subtract x from both sides and add 84 to both sides

36 = x

 

CPhill Sep 2, 2014

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