Ответ:

  1. \(0{,}5\sqrt{8100}-\frac14\sqrt{64}=0{,}5\cdot90-\frac14\cdot8=45-2=43.\)

  2. \(\sqrt{0{,}49\cdot25}=\sqrt{12{,}25}=3{,}5.\)

  3. \(\sqrt{5^6\cdot2^2}=\sqrt{(5^3\cdot2)^2}=5^3\cdot2=250.\)

  4. \(\frac{\sqrt{18}}{\sqrt2}-\frac{\sqrt{27}}{\sqrt3}=\sqrt9-\sqrt9=3-3=0.\)

Ответ: 1) 43; 2) 3,5; 3) 250; 4) 0.