\[\boxed{\text{4.\ 294}}\]
\[x - y\]
\[\textbf{а)}\ x - y = - 8\]
\[x = - 16;\ \ y = - 8.\]
\[\textbf{б)}\ x - y = 4,3\]
\[x = - 4;\ \ y = - 8,3.\]
\[\textbf{в)}\ x - y = 0\]
\[x = - 5;\ \ y = - 5.\]
\[\textbf{г)}\ x - y = - \frac{1}{4}\]
\[x = - \frac{3}{4};\ \ y = - \frac{1}{2}.\]
\[\textbf{д)}\ x - y = 1\]
\[x = - 8;\ \ y = - 9.\]
\[\textbf{е)}\ x - y = 0,01\]
\[x = - 9;\ \ y = - 9,01.\]