Question 687341
4x + 8y =20
-4x + 2y =30


You are gonna get rid of one of the variables. In this case x because it's the easiest. 

4x + 8y =20
-4x + 2y =30
The x's cancel out leaving you:
8y=20
2y=30
Then you add:
10y=50
Then Divide:
y=5
Then to find x, you get rid of the y.
4x + 8y =20
-4x + 2y =30
I make the 8 negative so I have a positive x, and a negative 16 to cancel out the y.
2( 4x + 8y =20)
-8(-4x + 2y =30)
8x + 16y= 40
32x - 16y =-240
Then you add.
40x = -200
x=-5 
Hope this makes sense! (: