Ответ:

  1. \(2^{20}:(2^8)^2=2^{20-16}=2^4=16\).
  2. \((11^3)^4:(11^5)^2=11^{12-10}=11^2=121\).
  3. \(7^9\cdot(7^2)^6:7^{19}=7^{9+12-19}=7^2=49\).
  4. \(16^2:8=(2^4)^2:2^3=2^{8-3}=2^5=32\).
  5. \(\frac{10^{17}\cdot(10^2)^3}{(10^3)^4\cdot10^9}=10^{17+6-12-9}=10^2=100\).
  6. \(\frac{9^3\cdot81^2}{3^{12}}=\frac{(3^2)^3\cdot(3^4)^2}{3^{12}}=3^{6+8-12}=3^2=9\).