[OkashiAddict]

I have a method but whenever I substitute my answer for x it doesn't balance on both sides so I don't know what I'm doing wrong...

Here is the question:

3x+2/4 - 7 = 5/8


This was what I did:
1) found the LCM = 8
first multiplied everything by 8 so that:

24x+16/4-56 = 5

And then multiplied everything by 4 so that:

96x +64 -224 = 20

96x -160 = 20

96x = 20+160

96x = 180

x = 1.875

But when substituted for x, it doesn't equal 5/8 (0.625) ?

Please help! I have a lot more questions after this to work on so just need an example to help me.
Thank you

[elldeegee]

is your orignal question
?

[Azzura]

you'll kick yourself if I show you the mistake....

[OkashiAddict]

(Original post by elldeegee)
is your orignal question
?

no, the 4 is under both 3x+2 but not the -7.

[Azzura]

(Original post by OkashiAddict)

24x+16/4-56 = 5

And then multiplied everything by 4 so that:

96x +64 -224 = 20

It was right until this point. 16/4 =/= 64

16/4 = 4

[OkashiAddict]

(Original post by Azzura)
you'll kick yourself if I show you the mistake....

Please tell me!

[Azzura]

(Original post by OkashiAddict)
Please tell me!

see above post

[OkashiAddict]

(Original post by Azzura)
It was right until this point. 16/4 =/= 64

16/4 = 4

Oh no, it's not 2/4

[elldeegee]

(Original post by OkashiAddict)
24x+16/4-56 = 5

And then multiplied everything by 4 so that:

96x +64 -224 = 20

This is wherre your problems lie.
when multiplying by 4, you don't need to multiply the 16 by 4 (Just like above, you didn't multiply the 5 on the RHS by 8)
So you should just get 96x +16 -224 = 20

It is also worth noting that because 16/4 = 4, there is no real need to multiply through by 4.

[Azzura]

x = 2.375

[OkashiAddict]

(Original post by elldeegee)
This is wherre your problems lie.
when multiplying by 4, you don't need to multiply the 16 by 4 (Just like above, you didn't multiply the 5 on the RHS by 8)
So you should just get 96x +16 -224 = 20

It is also worth noting that because 16/4 = 4, there is no real need to multiply through by 4.

Ohhh I see because they're the same kind of term? Why is this? And does this apply all the time for these kinds of questions?
Thank you

[elldeegee]

(Original post by OkashiAddict)
no, the 4 is under both 3x+2 but not the -7.

Ignore what i had said before.

As your original question wasnt laid out very well, did you have ?

[Azzura]

is this A level or GCSE?

[OkashiAddict]

(Original post by elldeegee)
Ignore what i had said before.

As your original question wasnt laid out very well, did you have ?

Yes, that's the one!

[OkashiAddict]

(Original post by Azzura)
is this A level or GCSE?

GCSE... I think... well I'm in year 10

[Azzura]

(Original post by OkashiAddict)
GCSE... I think... well I'm in year 10

yeah then it's GCSE

[elldeegee]

(Original post by OkashiAddict)
Yes, that's the one!

So you have

This bit:

24x+16/4-56 = 5

is correct, except you SHOULD write it as :
(i realise you may be unable to use the latexing format on here, but when laying it out on paper, it is easy to make mistakes if you don't lay it out like this)

Spoiler:

Show

when showing it on here without using latex, write (24x + 16)/4 -56 = 5 in order to make it clear what is in the fraction and what isn't

Again, it is here where the mistake was made:

And then multiplied everything by 4 so that:
96x +64 -224 = 20

and the use of brackets would have made it much more easier

multipply through by 4, so the numerator stays the same, but multiply all other terms by 4:



carry on from here.

[OkashiAddict]

(Original post by elldeegee)
So you have

This bit:
is correct, except you SHOULD write it as :
(i realise you may be unable to use the latexing format on here, but when laying it out on paper, it is easy to make mistakes if you don't lay it out like this)

Spoiler:

Show

when showing it on here without using latex, write (24x + 16)/4 -56 = 5 in order to make it clear what is in the fraction and what isn't

Again, it is here where the mistake was made:

and the use of brackets would have made it much more easier

multipply through by 4, so the numerator stays the same, but multiply all other terms by 4:



carry on from here.

So I only multiply by 4 to cancel out the denominator, but not the other terms? I don't really understand... could you please be clearer?

Thanks for your help so far

[elldeegee]

(Original post by Azzura)
It was right until this point. 16/4 =/= 64

16/4 = 4

You had actually misunderstood what it was he was doing so he wasn't saying that 16/4 = 64, he was saying that as he was multiplying through by 4, 16 x 4 =6 :

(Original post by elldeegee)
This is wherre your problems lie.
when multiplying by 4, you don't need to multiply the 16 by 4 (Just like above, you didn't multiply the 5 on the RHS by 8)
So you should just get 96x +16 -224 = 20

It is also worth noting that because 16/4 = 4, there is no real need to multiply through by 4.

[Azzura]

(Original post by elldeegee)
So you have

This bit:
is correct, except you SHOULD write it as :
(i realise you may be unable to use the latexing format on here, but when laying it out on paper, it is easy to make mistakes if you don't lay it out like this)

Spoiler:

Show

when showing it on here without using latex, write (24x + 16)/4 -56 = 5 in order to make it clear what is in the fraction and what isn't

Again, it is here where the mistake was made:

and the use of brackets would have made it much more easier

multipply through by 4, so the numerator stays the same, but multiply all other terms by 4:



carry on from here.

x = 9.5