Answer:
4 [Yes, really]
Explanation:
(8/64)^-2/3 [Wow]
(1/8)^-2/3 [Simplify 8/64 to 1/8]]
(8^-1)^-2/3 [Reformat (1/8) to 8^-1]
8^(-1*(-2/3)) [Rule of exponents: When an exponent is raised to another exponent, multiply the exponents.]
8^(2/3) [Simplify (-1(-2/3)) to (2/3)]
64^(1/3) [8^(2/3) means square the 8 and then take the cube root]
4 [The cube root of 64 is 4 (4*4*4 = 64]