One number or word is missing in the statement.
Assume you mean
"what is the log base 4 of 64?"That is:

Since,
logarithm is the inverse function of exponential, another way to say that is
to what exponent must be raised 4 to make 64?This is, find x such that
4 ˣ = 64Since 64 is 4³,
the answer would be 3. If the question were
"what is the log base 2 of 64?" then other way to say it is
to what number must be raised 2 to make 64?And the answer is found making:
2ˣ = 64
2ˣ = 2⁶Therefore,
x = 6.