[tex]a) \ log_{5}5 + log_{5}1 = log_{5}(5\cdot1) = log_{5}5 = log_{5}5^{1} = 1\\\\\\b) \ log_{6}1 - log_{\frac{1}{4}}0,25 = log_{6}6^{0} - log_{\frac{1}{4}}\frac{1}{4} = 0 - log_{\frac{1}{4}}(\frac{1}{4})^{1} = 0-1 = -1\\\\\\c)\\x = 0,999 ...\\\\10x = 9,999 ...\\\\10x - x = 9,999 ... - 0,999 ...\\\\9x = 9\\\\x = 1\\\\log_{7}(0,9) = log_{7}1 = log_{7}7^{0} = 0[/tex]
