Respostas

2013-11-12T11:13:31-02:00
X-7=25
x=25-7
x=18 meninos
y=25-18
y=7 meninas
5 2 5
2013-11-12T11:29:53-02:00
X+Y=25
X-Y=7

CANCELA O Y, POIS SÃO OPOSTOS.
2X=32                                          X+Y=25  
X=16                                           16+Y=25
                                                   Y=25-16
                                                     Y=9
5 4 5