Solving Simple Equations... please help!?!?

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locke - 18 Jul 2009 07:26 GMT

Trying to get back into the swing of mathematics and realizing how
much I've forgotten is really frustrating. I have been working this
problem and researching for two days now with no luck.

Problem 1:
6x + 4 = 2x + 12

Answer = 2

Problem 2:
7x - 3 = 4x - 27

Answer = -8

I understand how to solve for problem 1, but using the same basic
principles for problem 2, I can not figure out how they got -8.

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William Elliot - 18 Jul 2009 07:44 GMT

> Problem 2:
> 7x - 3 = 4x - 27
[quoted text clipped - 3 lines]
> I understand how to solve for problem 1, but using the same basic
> principles for problem 2, I can not figure out how they got -8.

Show us each step you've taken.

What do you get? -10?

What is -27 - (-3) ?

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locke - 18 Jul 2009 08:33 GMT

> > Problem 2:
> > 7x - 3 = 4x - 27
[quoted text clipped - 9 lines]
>
> What is -27 - (-3) ?

7x - 3 = 4x - 27
Step 1: 7x + 4x - 3 = 4x + 4x - 27
Step 2: 11x + -3 = 27
Step 3: 11x + -3 - -3 = 27 - -3
Step 4: 11x = 24

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William Elliot - 18 Jul 2009 09:59 GMT

>>> Problem 2:
>>> 7x - 3 = 4x - 27
[quoted text clipped - 8 lines]
> 7x - 3 = 4x - 27
> Step 1: 7x + 4x - 3 = 4x + 4x - 27

> Step 2: 11x + -3 = 27

Mistake. 2 does not follow from 1 for two reasons.

> Step 3: 11x + -3 - -3 = 27 - -3
> Step 4: 11x = 24

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Brian M. Scott - 18 Jul 2009 10:02 GMT

On Sat, 18 Jul 2009 00:33:02 -0700 (PDT), locke
<mcrosby32@gmail.com> wrote in
<news:f989a9a7-34c1-44af-880c-882993f0dc27@w41g2000yqb.googlegroups.com>
in alt.algebra.help:

>>> Problem 2:

>>> 7x - 3 = 4x - 27

>>> Answer = -8

>>> I understand how to solve for problem 1, but using the same basic
>>> principles for problem 2, I can not figure out how they got -8.

>> Show us each step you've taken.

>> What do you get? -10?

>> What is -27 - (-3) ?

> 7x - 3 = 4x - 27
> Step 1: 7x + 4x - 3 = 4x + 4x - 27
> Step 2: 11x + -3 = 27

Oops! 4x + 4x = 8x, not 0. In Step 1 you needed to
*subtract* 4x from each side (or add -4x to each side),
getting 7x - 4x - 3 = 4x - 4x - 27. There's another error
in Step 2 as well: how did -27 suddenly turn into 27?

Correctly simplifying the righthand side of

7x - 4x - 3 = 4x - 4x - 27

gives you 3x - 3 = -27.

Can you take it from there?

[...]

Brian

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Frederick Williams - 18 Jul 2009 10:29 GMT

> Problem 2:
> 7x - 3 = 4x - 27
[quoted text clipped - 3 lines]
> I understand how to solve for problem 1, but using the same basic
> principles for problem 2, I can not figure out how they got -8.

I would rather say 'Answer: x = -8' rather 'Answer = -8'. Anyhow, I
would proceed like this:

7x - 3 = 4x - 27

7x - 4x = -27 - (-3)

3x = -24

x = -8.

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Math Forum / Mathematics / Algebra Help / July 2009

Solving Simple Equations... please help!?!?