Question 1189981
2x+y=5
2y=2x-8 ---> y = x-4
-------------
2x+y=5
2x + (x-4) = 5
3x = 9
x = 3
----
y = x-4
y = -1
=========================
This is gibberish.  Which variable is the "first variable?"
---------
Find the first variable and isolate it. then solve for that variable.

Solve for the second variable 

Find the numerical value of the first variable

Check your solution