Respostas

2013-11-21T11:16:28-02:00
X+y = 13
x-y = 9

x+x+y-y = 13+9
2x = 22
x = 22/2
x = 11

11+y = 13
y = 13-11
y = 2
2013-11-21T11:18:38-02:00
X + y = 13
x - y = 9

2x = 22
x = 22/2
x = 11

substituindo para encontrar o Y
x + y = 13
11 + y = 13
y = 13 - 11
y = 2