Question

Using substitution, could someone please help me with this system?

–y + 3x = 6
y = –6x + 12

So far I've gotten:

Substituting the second equation into the first you get

-(-6x+12) + 3x = 6

Which can be solved for x after finding x you can use the second equation above directly to find y

Answer 1

Sounds like you know what you are doing .... What's the problem you are having?

Answer 2

Well, I had help with that part, but I can't figure out what to do next. I tried using my textbook, but it was a bit confusing, because they showed you what to do, but didn't explain it.

Answer 3

Ok, first let's distribute that -(-6x+12)
Can you do that?

Answer 4

-6x + -72?

Answer 5

Think of it this way:
(-)(-6x) & (-)(12)

Answer 6

Because negative times negative equals a positive 6x + -12?

Answer 7

yes, very good
so we have
6x-12+3x=6
What will you do next?

Answer 8

Add 6x and 3x?

Answer 9

correct
9x-12=6
now what?

Answer 10

Substitute for y from the other equation?

Answer 11

Let's try to solve for x.

Answer 12

Sorry, I was looking at my textbook, and thought that we were onto that step.

Answer 13

:-)
That's ok.

Answer 14

Okay, so how would I go about solving for x? Also, thank you for the medal.

Answer 15

We have x on one side, can we get non x-values on the other side?

Answer 16

You would add 12 + 6? Then get 18, divided by 9x would equal 2.

Answer 17

Excellent:
So x=2

Answer 18

Okay.

Answer 19

What are you going to do with that x=2?

Answer 20

You still there?

Answer 21

Substitute 2 for x in either equation and solve for y? Sorry, my computer is slow sometimes.

Answer 22

Heh I Understand.
You are correct, good job!

Answer 23

Thank you! So, -y + 3(2) + 6.

Answer 24

-y+3(2)=6

Answer 25

So, -y + 6 = 6.

Answer 26

correct

Answer 27

What would I do next?

Answer 28

same that you did when you had 9x-12=6 and solved for x. now we are going to it for y

Answer 29

6 - 6 = 0 So y, would be 0?

Answer 30

That is correct.

Answer 31

Then I would substitute 0for y, and get 0 + 6 = 6.

Answer 32

Correct:
So your Answer is:
X=2, y=0

Answer 33

As long as you get a correct statement when you plug them both back in, like you showed 6=6 and not get something like 7=6, then we would have a problem.

Answer 34

Okay, thank you some much for your help. If I could give you more than one medal I would.

Answer 35

Thank you,
It is nice to meet someone who wants to work out the problems and not just demand an answer.

Answer 36

I get what you mean, you are a very good teacher by the way.