Let logx3 = a ---> xa = 3 (equation 1)
Also: log81x = a ---> 81a = x (equation 2)
Substitue equation 2 into equation 1: (81a)a = 3 ---> 81a^2 = 3
Since 81 = 34 ---> (34)a^2 = 3 ---> 34a^2 = 31
---> 4a2 = 1
---> a2 = ¼
---> a = ½
Using equation 1: xa = 3 ---> x½ = 3 ---> x = 9