Okay, so some somehow I am just completely stuck this question. This is one of the examples from my textbook that I just can't solve and would probably help me solve the others I'm stuck on.
Solving by Substitution
3x+4y=12
2x+y=10

I keep getting this:
3x+4(-2x+10)=12
3x-8x+40
-5x+40=12
-5x=-32
x=6.4
Am I missing something staring me in the face? Because the answer should be x=5.6

Question

Okay, so some somehow I am just completely stuck this question. This is one of the examples from my textbook that I just can't solve and would probably help me solve the others I'm stuck on.
Solving by Substitution
3x+4y=12
2x+y=10

I keep getting this:
3x+4(-2x+10)=12
3x-8x+40
-5x+40=12
-5x=-32
x=6.4
Am I missing something staring me in the face? Because the answer should be x=5.6

kewlgeek555 · Answer

Are you studying slopes and linear functions and stuff?

kewlgeek555 · Answer

Because to me that looks lie the standard form of a linear function, which is Ax - By = C.

anonymous · Answer

Well, it's in the Linear Systems Chapter under Solving Systems Algebraically.

anonymous · Answer

I should note, this is Algebra 2 if that helps.

kewlgeek555 · Answer

Okay then.  I think what they mean is to find x first then y.  This is how you do it!:$$3x+4y=12$$$$3x+4(0)=12$$$$3x=12$$$$12\div3=x$$$$4=x$$Now, you are not finished yet.  All you have to do next is put it in a coordinate plane thingie:  (4, 0).

Now - did you see what I did with the y?  I just made it zero.  Do the same thing with x, when finding y.  Try to do it yourself!  :-)

kewlgeek555 · Answer

And OMG, Algebra II.  I am in Algebra I, but I just finished a chapter called "Linear Functions".  But I guess it would also be linear systems because I also learned linear models, linear equations, etc...

kewlgeek555 · Answer

Please tell me when you are done.

kewlgeek555 · Answer

...Or if you need assistance.

kewlgeek555 · Answer

I'll tell you what to do after you solve for y.

anonymous · Answer

Doing it on some paper, just a sec.

anonymous · Answer

Okay, well I see what you're saying but this is a textbook example, and it is telling me that x=5.6, and somehow I've manged to get x=6.4 and x=-1.6 the two times I solved it. Haven't even gotten to y yet. That is the whole issue.

kewlgeek555 · Answer

Hm.  So x HAS to equal 5.6?  Well, if x = 5.6, can't you plug in 5.6 and then solve for y?  Or is 5.6 the answer?

anonymous · Answer

5.6 is x which I then need to use to find y, I think I see where I went wrong so I'm going to try again real quick.

kewlgeek555 · Answer

Okay.  :-)

anonymous · Answer

Figured out where I went wrong, 12-40=-28, not 32. Makes a big difference and 4*10 does not =4. Moment of stupidity. Got it now, thanks for the help lol.

kewlgeek555 · Answer

Okay, you are welcome.  :-D