We have to solve: (0.25)^(x-4)=<(1/16)^x
(0.25)^(x-4)=<(1/16)^x
=> (1/4)^(x- 4) =< (1/16)^x
=> (1/4)^(x- 4) =< (1/4)^2x
As (1/4) is less than 1, we have 1/ 4 > (1/4^2)
Similarly, we can say (x- 4) => 2x
=> x - 2x => 4
=> -x => 4
=> x =< -4
Therefore x <= -4.