Respostas

2014-08-17T13:18:32-03:00
2x-y=7
-y=7-2x   (-1)
y=-7+2x

x-(y+5)=3x+2
x-y-5=3x+2
x-(-7+2x)-5=3x+2
x+7-2x-5=3x+2
x-2x-3x=-2-7+5
x-5x=-9+5
-4x=-4
x=-4
    -4
x=1