Ответ:

  1. \(x=5-y\), \(y=5-x\).
  2. \(x=y\), \(y=x\).
  3. \(x=y+3\), \(y=x-3\).
  4. \(x=3y-6\), \(y=\frac{x+6}{3}\).
  5. \(x=\frac{y-3}{2}\), \(y=2x+3\).
  6. \(x=-5y\), \(y=-\frac{x}{5}\).
  7. \(x=\frac{2y}{3}\), \(y=\frac{3x}{2}\).
  8. \(x=\frac{-10-2y}{5}=-2-\frac{2}{5}y\), \(y=-5-\frac{5}{2}x\).
  9. \(x=-1.4-\frac{7}{4}y\), \(y=-0.8-\frac{4}{7}x\).