8^x=1/64
By the equations for logarithm definition we have that
[color=#0a971e]x[/color]=log[color=#c51414]8[/color](1/64)=log[color=#c51414]8[/color](1)-log[color=#c51414]8[/color](8^2)=-2*log[color=#c51414]8[/color](8)=[color=#0a971e]-2[/color]