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April 13th, 2014, 04:52 AM   #1
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fraction and bracket equation

Hi,

I have attempted to work this out (several times).
If someone who knows what their doing can look at it I will be happy.
The equation is: 3/7(x - 2) = 2

Multiply out fraction:
3/7 X 3 (x - 2) = 2 X 7

Simplify:
7(x - 2) =14

Multiply out brackets:
7 X x - 2 = 14

Remove 2:
7x = 14

Remove 7:
x = 6

So 3/7(6-2) = 1.7
Would this round to 2.
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April 13th, 2014, 05:35 AM   #2
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This is a joke, right?

You managed to make an unheard-of error in every step!
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April 13th, 2014, 08:47 AM   #3
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Yes, its not funny. I am very bad at maths.
It actually really upsets me I am not able to use maths well.
If you give me a hint of how to start I will get back to you.

Thanks.
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April 13th, 2014, 12:35 PM   #4
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Math Focus: Abstract algebra
For a start you need to write your equations clearly to avoid confusion. For instance, does 3/7(x - 2) mean $\displaystyle \frac3{7(x-2)}$ or $\displaystyle \frac37(x-2)$? From what you wrote at the end of your post
Quote:
Originally Posted by Rob158 View Post
3/7(6-2) = 1.7
I should say it’s $\displaystyle \frac37(x-2)$.

Let’s start with where you made your first mistake:
Quote:
Originally Posted by Rob158 View Post
Multiply out fraction:
$\color{red}{\text{3/7 X 3}}$ (x - 2) = 2 X 7
You want to multiply both sides by 7. The part I’ve highlighted in red is incorrect. Can you rectify it?
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April 16th, 2014, 02:13 AM   #5
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Quote:
Originally Posted by Olinguito View Post
For a start you need to write your equations clearly to avoid confusion. For instance, does 3/7(x - 2) mean $\displaystyle \frac3{7(x-2)}$ or $\displaystyle \frac37(x-2)$? From what you wrote at the end of your postI should say it’s $\displaystyle \frac37(x-2)$.

Let’s start with where you made your first mistake:

You want to multiply both sides by 7. The part I’ve highlighted in red is incorrect. Can you rectify it?
Thanks for your reply.

Yes it is how you have done it but I don't know how to put in the fraction signs.

I have just copied your codes in just now.

The equation is:
$\displaystyle \frac37(x-2)$ = 2

Multiply out fraction:
3 (x -2) = 14

Multiply out brackets:
3x -6 = 14

Add 6:

3x = 14

Divide by 3:

x = 6.66...

Round to 6.7?

Check:

$\displaystyle \frac37(6.7 -2)$. = 2

What are your thoughts on this? I keep getting decimal numbers but don't know if this is right?

Thanks.
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April 16th, 2014, 03:11 AM   #6
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Your working is almost perfect. The only mistake you made is here:
Quote:
Originally Posted by Rob158 View Post
3x -6 = 14

Add 6:

3x = 14
The right-hand side should be $14+6=20$ so the answer should be $x=\dfrac{20}3$. But everything else you did was correct. Well done!

By the way, if you don’t like decimal numbers you can always leave your answer as a fraction.
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April 16th, 2014, 05:01 AM   #7
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Quote:
Originally Posted by Rob158 View Post
Thanks for your reply.

Yes it is how you have done it but I don't know how to put in the fraction signs.

I have just copied your codes in just now.

The equation is:
$\displaystyle \frac37(x-2)$ = 2

Multiply out fraction:
3 (x -2) = 14

Multiply out brackets:
3x -6 = 14

Add 6:

3x = 14

Divide by 3:

x = 6.66...

Round to 6.7?

Check:

$\displaystyle \frac37(6.7 -2)$. = 2

What are your thoughts on this? I keep getting decimal numbers but don't know if this is right?

Thanks.
When using an operation, and dealing with an equation you always have to do the same to both sides.
When multiplying out the fraction, you indeed do this. But, when adding 6 to the left hand side, you are not adding 6 to the right hand side.

There's nothing wrong with having a fraction as an answer, you don't necessarily have to round your answer. Also, note that only the fraction will be the exact answer.

Last edited by jyrdo; April 16th, 2014 at 05:03 AM.
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April 17th, 2014, 11:03 AM   #8
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Many thanks.

I see now I have been missing out a lot of steps in doing the calculation.
I can only get better with practice.

Kind regards.
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