Respostas

2013-10-17T19:07:45-03:00
7x + 1 - 5x = 9
7x - 5x = 9 - 1
2x = 8
x = 8 : 2
x = 4
3 4 3
2013-10-17T21:07:02-03:00
7x + 1 - 5x = 9 => 7x - 5x = 9 - 1 => 2x = 8 

Sendo 2x = 8, basta fazer 8:2 que teremos X. 
8:2 = 4  => X = 4