I need help on linear equations solving with substitution I need to know what to do as I am stuck.

[Monsterscore]

 

[tkhunny]

You have 8x = -2 - 2y
You substituted y = -2 - 2y

Simplify/Rearrange/Manipulate: 8x = -2 - 2y ==> x = (-2 - 2y)/8 = (-1 - y)/4
Substitute: 5(x) + y = 4 ==> 5((-1=y)/4) + y = 4

Additional Commentary:
That may have been the hardest way possible:
1) 8x + 2y = -2 ==> 4x + y = -1 ==> y = -1 - 4x
2) 5x + y = 4 ==> 5x + (-1 - 4x) = 4

More practice. You will begin to see more convenient ways to proceed.

 

[jalexandre]

I usually first look at both equations for a variable with a coefficient of 1, then isolate that variable. If you are lucky enough to have an equation with a variable whose coefficient is 1, it makes the problem a little easier.

In the second equation here, 5x+y=4, the y has a coefficient of 1. You can isolate the y in one step.

5x+ y= 4
-5x -5x
y = 4 - 5x

Now that you have an expression that is equivalent to y, you can substitute (4-5x) for y into the first equation and solve for x.

8x = -2 - 2(5-5x)

Then once you solve for x, you can use it to solve for y.

 

[lookagain]

Now that you have an expression that is equivalent to y, you can substitute (4-5x) for y into the first equation and solve for x.

8x = -2 - 2(5-5x)

jalexandre, 1) inside your parentheses you have a typo, and 2) that last line
does not show the intended expression substituted into the first equation.
It shows it substituted into an altered equation.

Literally substitute the expression into the first equation. Then clear parentheses
while it is there. Those x terms will already be together for combining like terms
together. As it is, you have more work to do, because you have to bring your
x term back over after it is freed up from clearing parentheses on the right-hand side.

 

[jalexandre]

jalexandre, 1) inside your parentheses you have a typo, and 2) that last line
does not show the intended expression substituted into the first equation.
It shows it substituted into an altered equation.

Literally substitute the expression into the first equation. Then clear parentheses
while it is there. Those x terms will already be together for combining like terms
together. As it is, you have more work to do, because you have to bring your
x term back over after it is freed up from clearing parentheses on the right-hand side.

Yes, you're totally right. Probably should have been a little more careful proof-reading

y=4 - 5x

and

8x + 2(4 - 5x) = -2