\[7,8 - 3\frac{2}{9} = \frac{78}{10} - 3\frac{2}{9} = \frac{39}{5} - 3\frac{2}{9} =\]
\[= 7\frac{4^{\backslash 9}}{5} - 3\frac{2^{\backslash 5}}{9} =\]
\[= 7\frac{36}{45} - 3\frac{10}{45} = 4\frac{26}{45}.\]