\[\boxed{\mathbf{Проверочная\ работа\ №1.\ Нахождение\ целого\ по\ его\ части\ }}\]
\[\boxed{\mathbf{1.}}\]
\[\frac{8}{9}\ :4 = \frac{8}{9} \cdot \frac{1}{4} = \frac{2}{9}.\]
\[\boxed{\mathbf{2.}}\]
\[\frac{2}{3}\ :\frac{1}{2} = \frac{2}{3} \cdot 2 = \frac{4}{3} = 1\frac{1}{3}.\]
\[\boxed{\mathbf{3.}}\]
\[\frac{6}{7}\ :3 = \frac{6}{7} \cdot \frac{1}{3} = \frac{2}{7}.\]
\[\boxed{\mathbf{4.}}\]
\[\frac{3}{5}x = 15\]
\[x = 15\ :\frac{3}{5} = 15 \cdot \frac{5}{3}\]
\[x = 5 \cdot 5 = 25.\]
\[\boxed{\mathbf{5.}}\]
\[\frac{1}{2}x = \frac{3}{7}\]
\[x = \frac{3}{7}\ :\frac{1}{2} = \frac{3}{7} \cdot 2\]
\[x = \frac{6}{7}.\]
\[\boxed{\mathbf{6.}}\]
\[\frac{1}{3}x = 0,3\]
\[x = \frac{3}{10}\ :\frac{1}{3} = \frac{3}{10} \cdot 3\]
\[x = \frac{9}{10} = 0,9.\]
\[\boxed{\mathbf{7.}}\]
\[\frac{5}{12}\ :\frac{5}{6} = \frac{5}{12} \cdot \frac{6}{5} = \frac{1}{2}\]
\[Нет.\]
\[\boxed{\mathbf{8.}}\]
\[40\ :\frac{1}{8} = 40 \cdot 8 = 320\]
\[Да.\]