[tex]\displaystyle log_2x+log_4x=6 \\ log_4x= \frac{log_2x}{log_24} = \frac{log_2x}{log_22^2}= \frac{log_2x}{2log_22}= \frac{log_2x}{2} \\ log_2x+ \frac{log_2x}{2} =6 \\ 2log_2x+log_2x=12 \\ 3log_2x=12 \\ log_2x= \frac{12}{3} \\ log_2x=4 \\ log_2x=log_22^4 \\ x=2^4 \\ \boxed{x= 16} [/tex]