(3:(1-√6)-√6:(1+√6))(9-2√6)
= ( 3(1+√6) : ((1-√6)(1+√6))) - ( √6(1-√6) : ((1-√6)(1+√6))) ) x (9-2√6)
= ( 3(1+√6) : (1^2 - (√6)^2) ) - ( √6(1-√6) : ( (1^2-(√6)^2) ) ) x (9-2√6)
= ( (3 + 3√6) :(-5) ) - ( (√6 - 6) : (-5) ) ) x (9-2√6)
= (( 3+3√6 - √6 + 6) : (-5) ) x (9-2√6)
= (( 9 +2√6) : (-5)) x (9-2√6)
= ( (9 +2√6) x (9-2√6) ):(-5)
= ( 9^2 - (2√6)^2) : (-5)
= (81 - 24) : (-5) = - 57/5