I'm assuming the 18x is to the power of 2. To solve this you first rearrange it to 18x^2 - 15x-12 = 0
You can begin to factorize it by finding two numbers which add up to -15 and multiply to -216 . These two numbers would be -24 and 9.
You can now write the equation as 18x^2 - 24x + 9x -12= 0
then, 6x(3x-4) + 3(3x-4)
= (6x+3)(3x-4) =0
Then to find what x is either (6x-3)= 0 or (3x-4)= 0
Therefore 6x-3=0
6x=3
x=2
and when 3x-4=0
3x=4
x=4/3
Final Answers: x = 2 or 4/3