Respostas

2013-08-28T22:29:28-03:00
X+y=2
x-y=6

x+y=2 
  +
x-y=6

2x=8
x=8/2
x=4

4+y=2
y=2-4
y=-4

4+(-2)=2
4-(-2)=6
33 4 33