Respostas

2013-11-04T13:42:56-02:00
X+y=3
x-y=9

*corta -y com +y 
2x=12
x=12/6
x=2 


x+y=3
x+(2)=3
x=3-2
x=1

2013-11-04T13:46:33-02:00