log3(x)+log5(x)=log81(15)

Log(3)x +(log(3)x)/log(3)5=(1/4)(log(3)3 +log(3)5),(Log(3)x)(log(3)5+1)/log(3)5=(1/4)(1+log(3)5),Log(3)x=log(3)(5^(1/4)),x=5^(1/4)