You can put this solution on YOUR website! Is the 12 a multiplier, or a power, or should it be ^2?
If it's a multiplier then:
8x-(2x+6)12
8x-24x-72
-16x-72
x=-72/-16
x=9/2 ans.
-------------
If it's a ^2 then:
8x-(2x+6)^2
8x-(x^2+24x+36)
-x^2-24x+8x-36
-x^2-16x-36
x^2+16x+36 ans.