| 3x+18 | = 12 is really two equations in one because it just says the absolute value of 3x+18 is 12. The two equations are 3x+18=12 and 3x+18=-12. In the first equation 3x=-6 so x=-2; in the second 3x+18=-12, so 3x=-30 and x=-10. The question could have been framed: (3x+18)^2=144, and the answer would have still provided the same two solutions. The quadratic x^2+12x+20=0 has the same solutions and is the result of expanding (3x+18)^2=144: 9x^2+108x+180=0⇒x^2+12x+20=0. Choose the method you like best!