\(\sqrt{63} = \sqrt{9} ⋅ \sqrt{7} = 3 \sqrt{7} \text{.}\)

\(-3 \sqrt{18} = -3 ⋅ \sqrt{9} ⋅ \sqrt{2} = -3 ⋅ 3 ⋅ \sqrt{2} = -9 \sqrt{2} \text{.}\)

\(\sqrt{\frac{9}{16}} = {\sqrt{9} \over \sqrt{16}} = \frac{3}{4} \text{.}\)

\({56 \sqrt{280} \over 8 \sqrt{10}} = {56 \over 8} ⋅ {\sqrt{280} \over \sqrt{10}} = 7 \sqrt{28} = 7 ⋅ \sqrt{4} ⋅ \sqrt{7} = 7 ⋅ 2 ⋅ \sqrt{7} = 14 \sqrt{7}\)

\(\sqrt{\frac{63}{64}} = {\sqrt{63} \over \sqrt{64}} = {\sqrt{63} \over 8} = \frac{1}{8} \sqrt{63} = \frac{1}{8} ⋅ 3 ⋅ \sqrt{7} = \frac{3}{8} \sqrt{7} \text{.}\)