Respostas

2014-03-13T15:42:36-03:00
7x - 7x = 0

7x - 7x = x + 18
        0 = x + 18
        x = -18
2014-03-13T17:27:38-03:00
7x-7x=x+18
7x-7x-x=18
7x-8x=18
-x=18