6(x + 3) + 3x = - 18
First multiply out the brackets:
6(x + 3) + 3x = - 18
6x + 6(3) + 3x = - 18
6x + 18 + 3x = - 18
9x + 18 = - 18
Now you can subtract 18 from both sides of the equation:
9x + 18 = - 18
9x + 18 - 18 = - 18 - 18
9x = - 36
Now you can divide both sides of the equation by 9 to get x on it's own:
9x = - 36
(9x)/9 = (- 36)/9
x = - 4