Answer
$x=12$
Work Step by Step
Given: $x-6=\sqrt 3x$
Square both sides: $(x-6)^2=(\sqrt 3x)^2\\x^2-12x+36=3x\\x^2-15x+36=0$
Solve for x: $x=12 \lor x=3$
Check: $12-6=6=\sqrt 3(12)=6$
$3-6=-3\ne\sqrt 3(3)=3$
Hence, the solution is $x=12$; there is an extraneous solution.