\[\boxed{\mathbf{261\ (261)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ \frac{x}{17} < \frac{8}{51}\text{\ \ \ }\]
\[\frac{3x}{51} < \frac{8}{51}\]
\[3x < 8\]
\[\ x = 1;2.\]
\[2)\ \frac{x}{65} < \frac{1}{13}\text{\ \ \ \ \ \ }\]
\[\frac{x}{65} < \frac{5}{65}\]
\[x < 5\ \ \]
\[x = 1;\ \ 2;\ 3;\ \ 4.\]
\[3)\ \frac{x}{5} < \frac{3}{15}\]
\[\frac{3x}{15} < \frac{3}{15}\]
\[3x < 3\ \ \ \ \]
\[x = нет\ натуральных\ \]
\[значений.\]
\[4)\ \frac{1}{16} < \frac{x}{8}\]
\[\frac{1}{16} < \frac{2x}{16}\]
\[1 < 2x\]
\[x = 1,\ 2,\ 3\ 4 - любое\ \]
\[натуральное\ число.\]