\[\boxed{\mathbf{4.}\mathbf{46}}\]
\[\textbf{а)}\ 1 - \frac{4}{7} = \frac{3}{7} \cdot 2 = \frac{6}{7}\ :\frac{3}{7} =\]
\[= 2 - 1\frac{1}{3} = \frac{2}{3}\]
\[\textbf{б)}\ 2 - \frac{5}{9} = 1\frac{4}{9} = \frac{13}{9}\ :13 =\]
\[= \frac{1}{9} \cdot 9 = 1 + \frac{9}{13} = 1\frac{9}{13}\]
\[\textbf{в)}\ \frac{16}{17}\ :8 = \frac{2}{17} \cdot 17 = 2 - 1\frac{7}{8} =\]
\[= \frac{1}{8}\ :2 = \frac{1}{16}\]
\[\textbf{г)}\ 4,5 + 3,5 = 8\ :5 = 1,6 + 1,4 =\]
\[= 3 \cdot 2,2 = 6,6 - 0,01 = 6,59\]