\[\begin{array}{l} {\text{а) }}\sqrt {\sqrt[3]{{80}} - \sqrt[3]{{64}}} = \frac{1}{3} \cdot \left( { - \sqrt[3]{{100}} + 2\sqrt[3]{{10}} + 2} \right) \hfill \\ {\text{б) }}\sqrt {\sqrt[3]{{125}} - \sqrt[3]{{100}}} = \frac{1}{3} \cdot \left( {\sqrt[3]{{100}} + \sqrt[3]{{10}} - 5} \right) \hfill \\ \end{array}\]