Ответ:

  1. \(\frac{2\cdot5^4}{5^2}=2\cdot5^2=50\).
  2. \(\frac{3^8\cdot6^9}{3^7\cdot6^6}=3\cdot6^3=648\).
  3. \(5^{12+15-11-14}=5^2=25\).
  4. \(7^{19+11-21-6}=7^3=343\).