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  • Usuário do Brainly
2013-11-12T11:05:57-02:00
X - y = 72
x + y = 280
________________
2x = 352
x = 352/2
x = 176

x - y = 72
176 - y = 72
-y = 72 - 176
y = 104

Tirando a prova temos:
x - y = 176 - 104 = 72
x + y = 176 + 104 = 280
2013-11-12T11:33:42-02:00
X+Y=72
X-Y=280
CANCELA O Y, POIS SÃO OPOSTOS
2X=352                        X+Y=72
X=176                         176+Y=72
                                  Y=72-176
                                   Y=-104