ГДЗ по математике 6 класс Виленкин Часть 1, 2 Часть 2. Параграф 4. Действия с рациональными числами Задание 318

\[\boxed{\text{4.\ 318}}\]

\[\textbf{а)}\ \frac{x}{- 1,4} = \frac{- 7,3}{- 2,8}\]

\[x = - \frac{7,3 \cdot 1,4}{2,8} = - \frac{7,3 \cdot 14}{28} =\]

\[= - \frac{7,3}{2}\]

\[x = - 3,65.\]

\[\textbf{б)}\ \frac{- 8,4}{105} = - \frac{12,6}{x}\]

\[x = \frac{105 \cdot 12,6}{8,4} = \frac{105 \cdot 126}{84} =\]

\[= \frac{105 \cdot 3}{2} = \frac{315}{2}\]

\[x = 157,5.\]

\[\textbf{в)}\ \frac{- 2,5x}{14} = \frac{\frac{1}{7}}{- 30}\]

\[2,5x \cdot 30 = 14 \cdot \frac{1}{7}\]

\[75x = 2\]

\[x = \frac{2}{75}.\]

\[\textbf{г)}\ \frac{- 7\frac{1}{2}}{4\frac{1}{2}} = \frac{x}{\frac{3}{25}}\ \]

\[4\frac{1}{2}x = - 7\frac{1}{2} \cdot \frac{3}{25}\]

\[\frac{9}{2}x = - \frac{15}{2} \cdot \frac{3}{25}\]

\[\frac{9}{2}x = - \frac{9}{10}\]

\[x = - \frac{9}{10}\ :\frac{9}{2}\]

\[x = - \frac{9}{10} \cdot \frac{2}{9}\]

\[x = - 0,2.\]