\[\boxed{\mathbf{1350.еуроки - ответы\ на\ пятёрку}}\]
\[\textbf{а)}\ k = \frac{5}{2} = 2,5;\]
\[\textbf{б)}\ k = - \frac{3}{2} = - 1,5;\]
\[\textbf{в)}\ k = - \frac{7}{2} = - 3,5;\]
\[\textbf{г)}\ k = \frac{2}{9}.\]