You know what's up!

first: you can define x in terms of y or alternatively: define y in term of x

Lets say you have defined x in terms of y from the first equation.

Then you substitute your new definition of x (in terms of y) into the second equation.

This will give you a strightforwrd equation containing only numbers and terms containing y, which you can solve simply, giving you a result for y = a number.

Then, going back to the first equation you can substitute your number for y, and solve for x.

Pimps!

Yes. I'm aware of that. But, the problem is I still cannot solve it.
[ANSWER]
y = 1
x = 3

Please show me how to get to these anwers. I know the subsmethod, but I can't seem to solve this one.

Hi Vraces,
Why don't you show us what you have done and then we can explain where you are going wrong.

Would be easy to just do it so I can understand but fine.

x + y = 2

2x - 3y = 9

2x - 3( 2 - x) = 9
2x - 6 -3x = 9
Here's where I realize that x is suppose to be 3, but I can't seem to work and my brain starts flipping out.

[x = 3 | y = 1]

<img src="http://2.bp.blogspot.com/_cadI18MG4K4/TTXNp6uCJOI/AAAAAAAAAP0/SK6FYDPjBKw/s320/confused-man.jpg" alt="Me">

2x - 3( 2 - x) = 9
Here is your mistake
2x -3* 2 -3*-x = 9

2x - 6 +3x = 9

If you had shown us your working you would have got this answer in the first place.

Well Melody, it still doesn't make sense.


5x = 9??
9/5 = x = 1,8
x = 3

Your calculation is incomplete. Do you have something against giving the answer, or what is the deal?

Vraces:

I've been trying to solve this for a hundred years.

x + y = 2

2x - 3y = 9

Subsitionsrule or whatever it's called.

Okay, okay, I hear you.
y=2-x
2x - 3(2-x) = 9
2x-6+3x = 9
5x-6=9
5x=15
x=3
You really can finish it yourself now.

I am really sorry I made a mistake on my other answer. I will fix it up and change the colour where I make changes.

Can you tell why the [3(2-x)] didn't become -3x but instead +3x

Hi Vraces

The short version is that there is a minus sign in front of the 3 so it was not 3(2-x) but really -3(2-x)

-3(2-x) = -3*2-3*-x = -6+3x

For this whole question
2x - 3( 2 - x)
maybe it would help if you put an extra + in like this

2x +[ - 3( 2 - x) ]

I hope that helps

Yeah I got it. I thought -?(?-?) would be the same as ?(?-?). But now I know.
Thanks for helping me out!

You are very welcome. (It's a very common error and it is good that you have got it sorted)

Have a great day!