\[\boxed{\mathbf{1.}}\]
\[4 + \frac{2}{9} = 4\frac{2}{9}\]
\[2\frac{3}{5} + 6 = 8\frac{3}{5}\]
\[\frac{5}{7} + 3\frac{1}{7} = 3\frac{6}{7}\]
\[9\frac{5}{8} - 2 = 7\frac{5}{8}\]
\[5\frac{7}{10} - \frac{4}{10} = 5\frac{3}{10}\]
\[6\frac{2}{3} - \frac{2}{3} = 6\]
\[1\frac{3}{11} + 3\frac{6}{11} = 4\frac{9}{11}\]
\[7\frac{5}{13} - 2\frac{4}{13} = 5\frac{1}{13}\]
\[1 - \frac{5}{12} = \frac{12}{12} - \frac{5}{12} = \frac{7}{12}\]
\[\boxed{\mathbf{2.}}\]
\[\textbf{а)}\ 1\frac{3}{4} + 2\frac{2}{4} = 3 + \frac{5}{4} = 3 + 1\frac{1}{4} =\]
\[= 4\frac{1}{4}\]
\[\textbf{б)}\ 4 - 2\frac{5}{6} = 3\frac{6}{6} - 2\frac{5}{6} = 1\frac{1}{6}\]
\[\boxed{\mathbf{3.}}\]
\[\left( 3\frac{9}{14} + x \right) - 2\frac{5}{14} = 6\frac{7}{14}\]
\[3\frac{9}{14} + x = 6\frac{7}{14} - 2\frac{5}{14}\]
\[3\frac{9}{14} + x = 4\frac{2}{14}\]
\[x = 4\frac{2}{14} - 3\frac{9}{14}\]
\[x = 3\frac{16}{14} - 3\frac{9}{14}\]
\[x = \frac{7}{14}.\]
\[\boxed{\mathbf{4.}}\]
\[1 - все\ учебники.\]
\[1)\ 1 - \left( \frac{5}{18} + \frac{11}{18} \right) = \frac{18}{18} - \frac{16}{18} =\]
\[= \frac{2}{18}\ (часть) - учебников\ \]
\[передали\ старшим\ классам.\]
\[2)\ 400\ :2 \cdot 18 =\]
\[= 3600\ (учебников) -\]
\[привезли\ в\ школу.\]
\[Ответ:3600\ учебников.\]
\[\boxed{\mathbf{5.}}\]
\[(n - n\ :100 \cdot 30)\ :6 \cdot 5\ (квартир) -\]
\[двухкомнатные.\]