Answer
$6$
Work Step by Step
$\sqrt 3(\sqrt {27}-\sqrt 3)$
=$\sqrt 3\times\sqrt {27}-\sqrt 3\times\sqrt 3$
=$(\sqrt 3\times\sqrt {9\times3})-(\sqrt 3\times\sqrt 3)$
=$(\sqrt 3\times3\sqrt {3})-(3)$
=$(3\times\sqrt 3\times\sqrt {3})-(3)$
=$3(3)-3$
=$9-3$
=$6$
