28) 11 82 4 =

$$\frac{1}{8} \cdot (\frac{1}{2})^4 = \frac{1}{2^3} \cdot \frac{1}{2^4} = \frac{1}{2^{3+4}} = \frac{1}{2^7} = \frac{1}{128}$$

Ответ: 1/128