Let's look at log₄(0.25):
It will be easy to write the log₄ if we can write 0.25 as 4ⁿ (that's expressing 4 to some power n)
because the log then is that power n
It happens that 0.25 = 1/4 = 4⁻¹
So we are really looking at log₄ (4⁻¹)
and this simplifies to just -1 (see that power, well that's the log!)
Now, you have to do the same thing with log₄(2)
and also log₄(64) (but this last one is very easy).
Having done that, you are well on the way ..... 
