\[\boxed{\mathbf{240\ (240)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ \frac{3}{8}\ и\ \frac{5}{12} \Longrightarrow \frac{9}{24}\ и\ \frac{10}{24}\]
\[2)\ \frac{2}{15}\ и\ \frac{3}{10} \Longrightarrow \frac{4}{30}\ и\ \frac{9}{30}\]
\[3)\ \frac{10}{17}\ и\ \frac{13}{34} \Longrightarrow \frac{20}{34}\ и\ \frac{13}{34}\]
\[4)\ \frac{4}{13}\ и\ \frac{3}{4} \Longrightarrow \frac{16}{52}\ и\ \frac{39}{52}\]
\[5)\ \frac{9}{14}\ и\ \frac{2}{21} \Longrightarrow \frac{27}{42}\ и\ \frac{4}{42}\]
\[6)\ \frac{1}{12}\ и\ \frac{1}{18} \Longrightarrow \frac{3}{36}\ и\ \frac{2}{36}\]
\[7)\ \frac{1}{9};\ \ \frac{1}{4}\ и\ \frac{1}{6} \Longrightarrow \frac{4}{36};\ \frac{9}{36}\ и\ \frac{6}{36}\]
\[8)\ \frac{3}{28};\ \frac{9}{14}\ и\ \frac{7}{8} \Longrightarrow \frac{6}{56};\ \frac{36}{56}\ и\ \frac{49}{56}\]
\[\boxed{\mathbf{240}\mathbf{.}}\]
\[5 \cdot 3 = 15\ м^{2} = 1500\ дм^{2} -\]
\[площадь\ прямоугольника.\]
\[Ответ:1500\ дм^{2}.\]