[tex]a) \ \sqrt\sqrt{400}:5} = \sqrt{20:5} = \sqrt{4} = 2\\\\b) \ \sqrt\sqrt{36}+\sqrt{100}} = \sqrt{6+10} = \sqrt{16} = 4\\\\c) \ \sqrt[3]{25\sqrt{25}} = \sqrt[3]{25\cdot5} = \sqrt[3]{5^{3}} = 5\\\\d) \ \sqrt\sqrt{8\sqrt[3]{2\sqrt[3]{64}}}} = \sqrt\sqrt{8\sqrt[3]{{2\cdot4}}}} = \sqrt\sqrt{8\sqrt[3]{8}}}} = \sqrt\sqrt{8\cdot2}}} = \sqrt\sqrt{16}} = \sqrt{4} = 2[/tex]
