SOLUTION: I need to solve the following problems using substitution. Do I need to get the y on one side by itself in order to solve the problem or can I use the x by itself on one side and u

Question 127891: I need to solve the following problems using substitution. Do I need to get the y on one side by itself in order to solve the problem or can I use the x by itself on one side and use substitution. Can the problem be -x=-2y+1 or does the x need to be positive before i can substitute it in the other equation. Im sorry if it sounds so confusing but Im a little confused. Thank you.
x-3y=9
-x+2y=1
If you have time would you be able to show me an example of elimination also. If not I understand. Thank you for your time.
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

Start with the given system of equations:

Now in order to solve this system by using substitution, we need to solve (or isolate) one variable. I'm going to solve for y.

So let's isolate y in the first equation

Start with the first equation

Subtract from both sides

Rearrange the equation

Divide both sides by

Break up the fraction

Reduce

---------------------

Since , we can now replace each in the second equation with to solve for

Plug in into the first equation. In other words, replace each with . Notice we've eliminated the variables. So we now have a simple equation with one unknown.

Distribute to

Multiply

Multiply both sides by the LCM of 3. This will eliminate the fractions (note: if you need help with finding the LCM, check out this solver)

Distribute and multiply the LCM to each side

Combine like terms on the left side

Add 18 to both sides

Combine like terms on the right side

Divide both sides by -1 to isolate x

Divide

-----------------First Answer------------------------------

So the first part of our answer is:

Since we know that we can plug it into the equation (remember we previously solved for in the first equation).

Start with the equation where was previously isolated.

Plug in

Multiply

Combine like terms and reduce. (note: if you need help with fractions, check out this solver)

-----------------Second Answer------------------------------

So the second part of our answer is:

-----------------Summary------------------------------

So our answers are:

and

which form the point

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