20) $$(\frac{1}{2})^{-3} \cdot 4^{-1}$$

Let's calculate the value of the expression. $$(\frac{1}{2})^{-3} \cdot 4^{-1} = 2^3 \cdot \frac{1}{4} = 8 \cdot \frac{1}{4} = \frac{8}{4} = 2$$ Answer: 2