$ \frac {2}{3}=0.\dot {6},$$\frac {5}{8}=0.625,$
$\frac {15}{23}≈0.65217,$$\frac {10}{17}≈0.588235,$$\frac {12}{19}≈0.631579$
$ $因为$0.\dot {6}>0.65217>0.631579>0.625>0.588235,$
所以$\frac {2}{3}>\frac {15}{23}>\frac {12}{19}>\frac {5}{8}>\frac {10}{17}$