To simplify #(9+3sqrt6)/sqrt3#, we have to first rationalize denominator. Here as denominator is pure irrational number #sqrt3#, we multiply numerator and denominator both by #sqrt3#.
The fraction than becomes
#((9+3sqrt6)/sqrt3)*sqrt3/sqrt3# or
#(9sqrt3+3sqrt6*sqrt3)/(sqrt3*sqrt3)#, which simplifies to