Ответ:

а)

[tex] \frac{5x}{y} = 5 \times ( - 0.2) = - 1[/tex]

б)

[tex] \frac{y}{x} = {( \frac{x}{y} )}^{ - 1} = {( - 0.2)}^{ - 1} = { (- \frac{1}{5}) }^{ - 1} = - 5[/tex]

в)

[tex] \frac{x}{y} = - 0.2 \\ x = - 0.2y[/tex]

[tex] \frac{7x + y}{x - y} = \frac{7 \times ( - 0.2y) + y }{ - 0.2y - y} = \frac{ - 1.4y + y}{ - 1.2y} = \frac{ - 0.4y}{ - 1.2y} = \frac{4y}{12y} = \frac{1}{3} [/tex]