\[\boxed{\text{5.4}\text{3}\text{9.}}\]
\[5\frac{4}{5} = 2 + 3\frac{4}{5} = 2 + \frac{19}{5} = 2\frac{19}{5}\ \]
\[7\frac{1}{9} = 4 + 3\frac{1}{9} = 4 + \frac{28}{9} = 4\frac{28}{9}\ \]
\[9\frac{9}{19} = 6 + 3\frac{9}{19} = 6 + \frac{66}{19} =\]
\[= 6\frac{66}{19}\]