a) $$\sqrt{0,64} - \sqrt{0,04} = 0,8 - 0,2 = 0,6$$
б) $$3 \cdot \sqrt{\frac{48}{3}} = 3 \cdot \sqrt{16} = 3 \cdot 4 = 12$$
в) $$\sqrt{900} \cdot \sqrt{100} = 30 \cdot 10 = 300$$
г) $$3\cdot\sqrt[4]{\frac{9}{16}}+\sqrt{0,25} = 3\cdot\sqrt[4]{\frac{3^2}{2^4}}+\sqrt{\frac{1}{4}}= 3 \cdot \frac{\sqrt{3}}{2}+\frac{1}{2} = \frac{3\sqrt{3}+1}{2}$$