\[\boxed{\mathbf{Проверочная\ работа.\ Пропорция\ }}\]
\[\boxed{\mathbf{1.}}\]
\[\frac{18}{4} = \frac{27}{6}.\]
\[\boxed{\mathbf{2.}}\]
\[\frac{3}{5} = \frac{2}{7}.\]
\[\boxed{\mathbf{3.}}\]
\[1,5\ :2 = 4,5\ :6\]
\[Средние\ члены:2\ и\ 4,5.\]
\[\boxed{\mathbf{4.}}\]
\[\frac{2}{1,9} = \frac{3}{2,8}\]
\[Крайние\ члены:2\ и\ 2,8.\]
\[\boxed{\mathbf{5.}}\]
\[1,5\ :2 = 4,5\ :6\]
\[2 \cdot 4,5 = 1,5 \cdot 6\]
\[9 = 9\]
\[Верно.\]
\[\boxed{\mathbf{6.}}\]
\[2\ :1,9 = 3\ :2,8\]
\[2 \cdot 2,8 = 1,9 \cdot 3\]
\[5,6 \neq 5,7\]
\[Неверно.\]
\[\boxed{\mathbf{7.}}\]
\[x = \frac{20 \cdot 0,5}{5} = 4 \cdot 0,5\]
\[x = 2.\]
\[Да.\]
\[\boxed{\mathbf{8.}}\]
\[\mathbf{Да.}\]