\[14\frac{8}{23}+5\frac{15}{23}=19+1=20.\]
\[6\frac{1}{5}-2\frac{3}{5}=3\frac{3}{5}=\frac{18}{5}.\]
\[50:20-\frac{18}{5}:9=\frac{5}{2}-\frac{2}{5}=\frac{21}{10}=2.1.\]
Ответ: 2,1.