\[\boxed{\text{26\ (26).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[при\ \ x - y = 0,7:\]
\[\textbf{а)}\ 5 \cdot (x - y) = 5 \cdot 0,7 = 3,5\]
\[\textbf{б)}\ y - x = - (x - y) = - 0,7\]
\[\textbf{в)}\ \frac{1}{x - y} = \frac{1}{0,7} = 1\ :\frac{7}{10} =\]
\[= 1 \cdot \frac{10}{7} = \frac{10}{7} = 1\frac{3}{7}\]
\[\textbf{г)}\ \frac{x - y}{y - x} = \frac{x - y}{- (x - y)} = - \frac{0,7}{0,7} =\]
\[= - 1\]