Respostas

2014-03-11T12:17:45-03:00
12x + 9x= 3x + 90
12x + 9x - 3x= 90
18x= 90
x= 90/18
x= 5.
1 5 1
2014-03-11T12:42:43-03:00

12x+9x-3x-90=0
18x-90=0
18x=90
x=90/18
x=5