\[\boxed{\mathbf{1021}\mathbf{.}\mathbf{\ }}\]
\[1)\ x + 7\frac{4}{15} = 9\frac{7}{10}\text{\ \ \ \ \ }\]
\[x = 9\frac{7^{\backslash 3}}{10} - 7\frac{4^{\backslash 2}}{15} = 9\frac{21}{30} - 7\frac{8}{30}\]
\[x = 2\frac{13}{30}\]
\[Ответ:2\frac{13}{30}.\]
\[2)\ 8\frac{9}{14} - x = 4\frac{3}{7}\text{\ \ \ \ \ \ }\]
\[x = 8\frac{9}{14} - 4\frac{3^{\backslash 2}}{7} = 8\frac{9}{14} - 4\frac{6}{14}\]
\[x = 4\frac{3}{14}\]
\[Ответ:4\frac{3}{14}.\]
\[3)\ x - 3\frac{8}{9} = 5\frac{1}{12}\text{\ \ \ \ \ }\]
\[x = 5\frac{1^{\backslash 3}}{12} + 3\frac{8^{\backslash 4}}{9} = 5\frac{3}{36} + 3\ \frac{32}{36}\]
\[x = 8\frac{35}{36}\]
\[Ответ:8\frac{35}{36}.\]