Hi Jason;
FIRST EQUATION...3x+y=5
SECOND EQUATION...x+2y=0
Let's take the second equation and isolate x...
x=2y
FIRST EQUATION...
3x+y=5
[3(2y)]+y=5
6y+y=5
7y=5
y=5/7
FIRST EQUATION...
3x+y=5
3x+(5/7)=5
Let's eliminate annoying fractions and multiply both sides by 7...
7[3x+(5/7)]=5(7)
21x+5=35
21x=30
x=30/21=10/7
SECOND EQUATION, to verify results of first equation...
x+2y=0
(10/7)+[(2)(5/7)]=0
(10/7)+(10/7)=0
0=0
1/16/2014

Vivian L.