2√(2/3)＋√(1/6)－(1/5)√54
=2√(6/9)＋√(6/36)－(1/5)√[3²×6]
=(2/3)√6＋(1/6)√6－(3/5)√6
=[(2/3)＋(1/6)－(3/5)]√6
=(7/30)√6