$$log_{5} \sqrt{5\sqrt{5}} = log_{5} \sqrt{5 \cdot 5^{\frac{1}{2}}} = log_{5} \sqrt{5^{\frac{3}{2}}} = log_{5} (5^{\frac{3}{2}})^{\frac{1}{2}} = log_{5} 5^{\frac{3}{4}} = \frac{3}{4}$$
Ответ: 3/4