$\frac{14}{21}-\frac{11}{21}=\frac{3}{21}=\frac{1}{7}$

$4\frac{3}{7}-2\frac{1}{7}=2\frac{2}{7}$

$2-\frac{5}{10}=1\frac{5}{10}=1\frac{1}{2}$

$4-\frac{18}{23}=3\frac{5}{23}$

$9\frac{2}{11}-6\frac{1}{11}=3\frac{1}{11}$

$7\frac{19}{30}-2\frac{21}{30}=6\frac{49}{30}-2\frac{21}{30}=4\frac{28}{30}=4\frac{14}{15}$