SOLUTION: Hi. I have a test coming up and I'm studying for it. But I don't know how to solve it. Here is my question: For the following system, use the second equation to make a substitutio

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Question 999643: Hi. I have a test coming up and I'm studying for it. But I don't know how to solve it. Here is my question:
For the following system, use the second equation to make a substitution for x in the first equation.
x + 5 y - 10 = 0
x = 2 y - 8
What is the resulting equation in simplest form?
My options were
-3 y - 18 = 0
3 y - 18 = 0
7 y - 18 = 0
7 y + 18 = 0
I don't know which one please help. And thank you to who ever helps
Found 2 solutions by MathLover1, ikleyn:
Answer by MathLover1(20850) (Show Source):
You can put this solution on YOUR website!
...1st eq.
...2nd eq.
-----------------------------
make a substitution for x in the first equation
...1st eq....solve for

=>the resulting equation in simplest form
to find the solutions to the system solve for :

=> exact solution
now go back to 2nd eq., substitute and find
...2nd eq....write as

Answer by ikleyn(52786) (Show Source):
You can put this solution on YOUR website!
.
For the following system, use the second equation to make a substitution for x in the first equation.
x + 5*y - 10 = 0
x = 2*y - 8
-------------------------------------------------------------

The second equation just expresses x via y. Substitute it into the first equation. You will get

(2y -8) + 5y - 10 = 0.

Simplify and solve it for y.

7y = 18,

y = .

Now, substitute this value of y into the second equation of the original system. You will get

x = 2* - = . . .

Please complete calculations yourself.

Do not forget to check the solution after completing.