Chapter 4 - Exponential and Logarithmic Functions - Section 4.4 Logarithmic Functions - 4.4 Assess Your Understanding - Page 322: 95

$3$

$\because y=\log_a x \text{ is equivalent to } x= a^y$ $\therefore x = \log_4 64 \text{ is equivalent to } 64=4^x$ Solve the equation above using the rule $a^m=a^n\implies m=n$ to obtain: \begin{align*} 64&=4^x\\\\ 4^3&=4^x\\\\ 3&=x\end{align*}