B = \left( {3\sqrt 2 + \sqrt 6 } \right)\sqrt {6 - 3\sqrt 3 }= (3 + \sqrt 3 )\sqrt {12 - 6\sqrt 3 } = (3 + \sqrt 3 )\sqrt {(3 - \sqrt 3 )^2 } = (3 + \sqrt 3 )(3 - \sqrt 3 ) = 9 - 3 = 6