In this case the base is 2, n is the unknown whose logarithm, base 2, is 4.
[tex] log_{2} n = 4[/tex]
So, applying the properties of logarythms you get:
2^4 = n
This is, 2^4 = n is equivalent to your expression.
And, of course, you can find the value of n:
=> n = 2^4 = 2*2*2*2 = 16
