b) $\left(\frac{-64}{27}\right)^{-\frac{1}{3}}=$

Step 1 ：Find the cube root of the given fraction: \(\sqrt[3]{\frac{-64}{27}}\)

Step 2 ：Calculate the cube root: \(\frac{-4}{3}\)

Step 3 ：Take the reciprocal of the result since the exponent is -1/3: \(\left(\frac{-4}{3}\right)^{-1}\)

Step 4 ：Calculate the reciprocal: \(\frac{3}{-4}\)

Step 5 ：\(\boxed{\frac{-3}{4}}\)