Ответ:

  1. \(\dfrac{7x}{21y}=\dfrac{x}{3y}\).
  2. \(\dfrac{16ab}{4ac}=\dfrac{4b}{c}\).
  3. \(\dfrac{25m^3}{15m^6}=\dfrac{5}{3m^3}\).
  4. \(\dfrac{8ab^3c^2}{16a^2bc^3}=\dfrac{b^2}{2ac}\).
  5. \(\dfrac{48a^5b^7}{32a^3b^9}=\dfrac{3a^2}{2b^2}\).
  6. \(\dfrac{34m^9n^3}{54m^4n^7}=\dfrac{17m^5}{27n^4}\).

Ответ: 1) \(\dfrac{x}{3y}\); 2) \(\dfrac{4b}{c}\); 3) \(\dfrac{5}{3m^3}\); 4) \(\dfrac{b^2}{2ac}\); 5) \(\dfrac{3a^2}{2b^2}\); 6) \(\dfrac{17m^5}{27n^4}\).