solve for X

Exponent rules, 8^x = 9^x*3, so x = x = -log(3)/log(9/8)

IF you know how to do LOGs

(2³)^x  = 3^2x  _* 3

8^x      = ( 3²)^x *3

        = 9^x   * 3

(8/9)^x =  3      take log of both sides

x log (8/9) = log 3

x = log 3 / log(8/9) = -9.327