\[\boxed{\text{876.}\text{\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ \sqrt{2} + 5\ и\ 2 + \sqrt{5}\]
\[\sqrt{1} + 5 < \sqrt{2} + 5 < \sqrt{4} + 5\]
\[6 < \sqrt{2} + 5 < 7.\]
\[2 + \sqrt{4} < 2 + \sqrt{5} < 2 + \sqrt{9}\]
\[4 < 2 + \sqrt{5} < 5.\]
\[\sqrt{2} + 5 > 2 + \sqrt{5}.\]
\[\textbf{б)}\ \sqrt{3} - 4\ \ и\ 1 - \sqrt{5}\]
\[\sqrt{1} - 4 < \sqrt{3} - 4 < \sqrt{4} - 4\]
\[- 3 < \sqrt{3} - 4 < - 2.\]
\[1 - \sqrt{4} < 1 - \sqrt{5} < 1 - \sqrt{9}\]
\[- 1 > 1 - \sqrt{5} > - 2\]
\[- 2 < 1 - \sqrt{5} < - 1.\]
\[\sqrt{3} - 4 < 1 - \sqrt{5}\]
\[\textbf{в)}\frac{2\sqrt{3} + 23}{3}\ и\ 9\]
\[\sqrt{1} < \sqrt{3} < \sqrt{4}\]
\[1 < \sqrt{3} < 2.\]
\[2 \cdot 1 + 23 < 2\sqrt{3} +\]
\[+ 23 < 2 \cdot 2 + 23\]
\[25 < 2\sqrt{3} + 23 < 27\]
\[\frac{25}{3} < \frac{2\sqrt{3} + 23}{3} < 9.\]
\[\frac{2\sqrt{3} + 23}{3} < 9.\]
\[\textbf{г)}\frac{1 - \sqrt{15}}{12}\ \ и\ \ \left( - \frac{7}{8} \right)\]
\[- \sqrt{16} < - \sqrt{15} < - \sqrt{9}\]
\[- 4 < - \sqrt{15} < - 3.\]
\[\frac{1 - 4}{12} < \frac{1 - \sqrt{15}}{12} < \frac{1 - 3}{12}\]
\[- \frac{3}{12} > \frac{1 - \sqrt{15}}{12} > - \frac{2}{12}\]
\[- \frac{1}{4} > \frac{1 - \sqrt{15}}{12} > - \frac{1}{2}\]
\[- \frac{1}{2} = - \frac{4}{8}\]
\[- \frac{4}{8} > - \frac{7}{8}\]
\[\frac{1 - \sqrt{15}}{12} > - \frac{7}{8}.\]