to rationalise the denominator u times the numerator and denominator by the denominator so
(12-5√3)/√3 times by √3/√3 which is √12(12-5√3) divided by √3(√3) so now just times the brackets out making 12√3- (5x3) -because √3 x √3 is 3- divided by 3 - for the same reason
so the answer is (12√3-15)/3 which is 4√3-5
