Chapter 10 - Exponents and Radicals - 10.2 Rational Numbers as Exponents - 10.2 Exercise Set - Page 641: 79

$64$

Using the laws of exponents, the given expression, $ \left( 64^{3/4} \right)^{4/3} ,$ simplifies to \begin{array}{l}\require{cancel} 64^{\left( \frac{3}{4} \right) \left( \frac{4}{3} \right)} \\\\= 64^{\frac{12}{12}} \\\\= 64^{1} \\\\= 64 .\end{array}