Question

I am working on solving a systems of two linear equations in two variables using the substitution method... could someone help me on how to start this x+y=7
x-2y=-5

Answer 1

Try to isolate x in x+y=7, then substitute in x-2y=-5.

Answer 2

so would I start x=-y+7

Answer 3

then take that and substitute it x(y+7)-2y=5

Answer 4

yes. And then?

Answer 5

or is it x(-y+7)-2y=5

Answer 6

Actually,
(x)-2y=-5 becomes (-y+7)-2y=5
right?

Answer 7

so x goes away

Answer 8

Because x=-y+7 you substitute x by (-y+7).

Answer 9

Easy, isn't it?

Answer 10

yes..... thank you. I have had such a tough time with this stuff. Thank you so much

Answer 11

And then?
What is the solution?

Answer 12

ahmm do I multiply (-y+7) by -2y?

Answer 13

You are almost there.
(-y+7)-2y=-5 becomes
-y+7-2y=5 there is no multiplication

Answer 14

why did the -5 become a positve 5

Answer 15

sorry, I forgot
(-y+7)-2y=-5 becomes
-y+7-2y=-5 there is no multiplication

Answer 16

I think I have it... subtract -2 from 7

Answer 17

ok.. thank you

Answer 18

I understand it much better now... but that's how I get I get it and then forget it :)

Answer 19

try again

Answer 20

Only add or subtract like terms.
-y+7-2y=-5
-y-2y +7=-5
-3y +7=-5

Answer 21

?

Answer 22

do you want me to solve these equations?

Answer 23

I think you should watch some videos on Youtube.
Just search for "Systems Using Substitution" there, and you will understand better this subject.

Answer 24

ok.. thanks you... do they have the elimation method too.

Answer 25

There is a bunch of videos there that will help you.
Try it some time.

Answer 26

I will right now. ..... I really appreciate your help. thank you again

Answer 27

You're welcome.