Question

x - y = 2
2x + y = 4

Answer 1

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

Answer 2

Ola 

x - y = 2
2x + y = 4

3x = 6
x = 6/3 = 2

2 - y = 2
y = 0

.