Ответ:

Приводим дроби к общему знаменателю.

  1. \(\frac{x}{2}+\frac{y}{8}=\frac{4x}{8}+\frac{y}{8}=\frac{4x+y}{8}\).
  2. \(\frac{a}{b}-\frac{b^2}{a}=\frac{a^2}{ab}-\frac{b^3}{ab}=\frac{a^2-b^3}{ab}\).
  3. \(\frac{c}{4}-\frac{d}{12}=\frac{3c}{12}-\frac{d}{12}=\frac{3c-d}{12}\).
  4. \(\frac{8}{2x}-\frac{2}{8x}=\frac{32}{8x}-\frac{2}{8x}=\frac{30}{8x}=\frac{15}{4x}\).
  5. \(\frac{5x}{8y}+\frac{x}{4y}=\frac{5x}{8y}+\frac{2x}{8y}=\frac{7x}{8y}\).
  6. \(\frac{1}{5a}-\frac{8}{25a}=\frac{5}{25a}-\frac{8}{25a}=-\frac{3}{25a}\).
  7. \(\frac{17y}{24c}-\frac{25y}{36c}=\frac{51y}{72c}-\frac{50y}{72c}=\frac{y}{72c}\).
  8. \(\frac{3b}{4c}+\frac{c}{2b}=\frac{3b^2}{4bc}+\frac{2c^2}{4bc}=\frac{3b^2+2c^2}{4bc}\).

Ответ: \(\frac{4x+y}{8};\ \frac{a^2-b^3}{ab};\ \frac{3c-d}{12};\ \frac{15}{4x};\ \frac{7x}{8y};\ -\frac{3}{25a};\ \frac{y}{72c};\ \frac{3b^2+2c^2}{4bc}\).