Respostas

2013-11-21T15:25:09-02:00
  • Usuário do Brainly
2013-11-21T15:28:13-02:00
X+y=10  (3)
x-3y=-18

3x+3y=30
x-3y=-18

4x=12
x=12/4
x=3

x+y=10
y=10-x
y=10-3
y=7
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