\(\sqrt{1} = 1\)

\(\sqrt{36} = 6\)

\(\sqrt{225} = 15\)

\(\sqrt{25} + \sqrt{64} = 5 + 8 = 13\)

\(5 \sqrt{64} - 12 \sqrt{9} = 5 ⋅ 8 - 12 ⋅ 3 = 4\)

\(\sqrt{4} ⋅ \sqrt{81} = 2 ⋅ 9 = 18\)

\((-7 \sqrt{5})^{2} = (-7)^{2} ⋅ \sqrt{5}^{2} = 49 ⋅ 5 = 245 \text{.}\)

\((5 \sqrt{4} - 8) (5 \sqrt{4} + 8) = (5 \sqrt{4})^{2} - 8^{2} = 25 ⋅ 4 - 64 = 100 - 64 = 36 \text{.}\)

\((\sqrt{10})^{2} = 10 \text{.}\)

\(2 (\sqrt{5})^{2} = 2 ⋅ 5 = 10 \text{.}\)

\(\sqrt{15} - 9 \sqrt{15} = -8 \sqrt{15}\)

\(4 \sqrt{2} ⋅ 6 \sqrt{13} = 24 \sqrt{26}\)

\({\sqrt{35} \over \sqrt{5}} = \sqrt{7}\)

\({20 \sqrt{30} \over 5 \sqrt{10}} = {20 \over 5} ⋅ {\sqrt{30} \over \sqrt{10}} = 4 \sqrt{3}\)

\({4 \sqrt{54} \over \sqrt{6}} = 4 ⋅ {\sqrt{54} \over \sqrt{6}} = 4 ⋅ \sqrt{9} = 4 ⋅ 3 = 12\)