Question

For the following system, if you isolated x in the second equation to use the Substitution Method, what expression would you substitute into the first equation?

3x + y = 8
-x - 2y = -10

Answer 1

We isolate the x in the second equation by adding 2y on both sides then multiplying by (-1).

Answer 2

Can you do that @kaylamarie081 ? I'll walk you through if you can't.

Answer 3

I added 2y to both sides on the second equation and I got -x= 30. It doesn't look right though. Help me please

Answer 4

@math&ing001

Answer 5

I don't know where you got that 30 but this is the step by step :
-x - 2y = 10
+ 2y +2y
-x = 10 +2y
-x*(-1) = (10+2y)*(-1)
x= -10 - 2y
So the expression you'll substitute into the first equation is (-10-2y).

Answer 6

Can you help me with another one please

Answer 7

Solve the following system of equations.
x - y = 16
2x + y = 2

Answer 8

Ok but I will not solve it for you. You'll have to do the work.

Answer 9

Isolate x in the first equation. It's just like you're solving for x.

Answer 10

@kaylamarie081

Answer 11

OK, just a minute. I'm trying to solve it on paper.

Answer 12

Alright, take your time ^^

Answer 13

Am I doing it right so far

Answer 14

I get confused on these kinda equations.

Answer 15

Isolating x should give you x=16-y

Answer 16

Okay so I messed up at 2(16)+y=2?

Answer 17

Sorry I took so long, I was away :)

Answer 18

That's fine. :)

Answer 19

Actually you messed up on the first equation, and that's what got the second one wrong. If you replace the x with (16-y) on the second you should be fine.

Answer 20

:(

Answer 21

Where are you stuck ?

Answer 22

Confused about everything.. K so I have to solve that?^^^

Answer 23

Yep !

Answer 24

It IS right so far, go on =3

Answer 25

It equals 30?

Answer 26

Yeah !

Answer 27

You're awesome. Thank you so much. Defintley couldn't of done it without you!(:

Answer 28

Now we replace it on the first equation to find x.
x=16-y

Answer 29

K

Answer 30

Wait nvm. I need to find x not y

Answer 31

Exactly ! Because you already found y.

Answer 32

You went too far, all you have to do is replace y by its value in here :
x = 16-y = 16-30 = -14

Answer 33

In case you're still confused, here's what we did so far :

Answer 34

Thanks.

Answer 35

Welcome !

Answer 36

Could you help me on this word problem?

Answer 37

Well the distance doesn't change, so that's how you'll find the speed on still water.
Distance = 45 * 3 = speedonstillwater * 2
So speedonstillwater = 45*3/2