Respostas

2013-12-08T17:32:22-02:00
2013-12-08T17:34:52-02:00
3x+y=13
2x-y=12
5x=25
x=25/5
x=5 

encontrando o y

2.5-y=12
10-y=12
-y=12-10
-y=2(-1)
y=-2

2 3 2