Answer
$x=9$
Work Step by Step
Isolate the square root on one side. Then square both sides and put all terms on one side. Factor by trial and error to solve for $x$. One of the answers does not work.
$\sqrt {x}-3=x-9$
$(\sqrt x)^2=(x-6)^2$
$x=x^2-12x+36$
$x^2-13x+36=0$
$(x-4)(x-9)=0$
$x=4,9$
$\sqrt 4-3\ne4-9$
$x=9$
