\[\left( 19 - 8\frac{7}{8} \right) - \left( 4\frac{5}{6} - 2\frac{8}{9} \right) =\]
\[= \left( 18\frac{8}{8} - 8\frac{7}{8} \right) - \left( 4\frac{15}{18} - 2\frac{16}{18} \right) =\]
\[= 10\frac{1}{8} - \left( 3\frac{33}{18} - 2\frac{16}{18} \right) =\]
\[= 10\frac{1^{\backslash 9}}{8} - 1\frac{17^{\backslash 4}}{18} =\]
\[= 10\frac{9}{72} - 1\frac{68}{72} =\]
\[= 9\frac{81}{72} - 1\frac{68}{72} = 8\frac{13}{72}\]