18. \(\log_{0.5} 7 \cdot \log_7 2\)

\(\log_{0.5} 7 \cdot \log_7 2 = \frac{\log 7}{\log 0.5} \cdot \frac{\log 2}{\log 7} = \frac{\log 2}{\log 0.5} = \frac{\log 2}{\log (\frac{1}{2})} = \frac{\log 2}{-\log 2} = -1\). Ответ: -1