Question

x + 2y = 4
x - 2y = 0

Answer 1

x+2y=4
x-2y=0  

2x=4
 x= 4 
    2
x=2

2+2y=4
2y=4-2
2y=2
y= 2 
    2
y=1

Testar.....

2+2.1=
2+2=4

2-2.1=
2-2=0