Решение

1. $$\lg_4 2 + \lg_4 8 = \lg_4 (2 \times 8) = \lg_4 16 = 2$$
2. $$\log_8 4 + \log_8 16 = \log_8 (4 \times 16) = \log_8 64 = 2$$
3. $$\log_3 11 - \log_3 99 = \log_3 \frac{11}{99} = \log_3 \frac{1}{9} = -2$$
4. $$\log_{\frac{1}{2}} 7 - \log_{\frac{1}{2}} \frac{7}{16} = \log_{\frac{1}{2}} \frac{7}{\frac{7}{16}} = \log_{\frac{1}{2}} 16 = -4$$
5. $$\lg 190 - \lg 19 = \lg \frac{190}{19} = \lg 10 = 1$$
6. $$\log_{15} \sqrt[5]{225} = \log_{15} (225)^{\frac{1}{5}} = \log_{15} (15^2)^{\frac{1}{5}} = \log_{15} 15^{\frac{2}{5}} = \frac{2}{5}$$