a) $$sqrt{\frac{25}{64}} : \sqrt{56} \cdot \sqrt{14} = \frac{\sqrt{25}}{\sqrt{64}} : \sqrt{56 \cdot 14} = \frac{5}{8} : \sqrt{784} = \frac{5}{8} : 28 = \frac{5}{8} \cdot \frac{1}{28} = \frac{5}{224}$$
в) $$2(\sqrt{3})^2 = 2 \cdot 3 = 6$$
Ответ: а) $$\frac{5}{224}$$, в) $$6$$