(√54+√(1/6)/√2-√(1/27)
=√(54/2)+√[(1/6)/2]-√(1/27)
=√27+√(1/12)-√(1/27)
=√(3^2*3)+√(3/36)-√(3/81)
=3√3+√(3/6^2)-√(3/9^2)
=3√3+(√3)/6-(√3)/9
=(3+1/6-1/9)√3
=(55/18)√3