\(\sqrt{80} = \sqrt{16} ⋅ \sqrt{5} = 4 \sqrt{5} \text{.}\)

\(4 \sqrt{80} = 4 ⋅ \sqrt{16} ⋅ \sqrt{5} = 4 ⋅ 4 ⋅ \sqrt{5} = 16 \sqrt{5} \text{.}\)

\(\sqrt{1\frac{9}{16}} = \sqrt{\frac{25}{16}} = {\sqrt{25} \over \sqrt{16}} = \frac{5}{4} = 1\frac{1}{4} \text{.}\)

\({45 \sqrt{36} \over 9 \sqrt{3}} = {45 \over 9} ⋅ {\sqrt{36} \over \sqrt{3}} = 5 \sqrt{12} = 5 ⋅ \sqrt{4} ⋅ \sqrt{3} = 5 ⋅ 2 ⋅ \sqrt{3} = 10 \sqrt{3}\)