$\frac{2}{7}$ + $\frac{-4}{3}$ = $\frac{6}{21}$ +$\frac{-28}{21}$ =$\frac{6+(-28)}{21}$ = $\frac{-22}{21}$
$\frac{10}{3}$ . $\frac{9}{-5}$ =$\frac{5.2}{3}$ . $\frac{3.3}{-5}$ = $\frac{-2}{3}$
$\frac{-3}{7}$ : (-9)=$\frac{-3}{7}$:$\frac{-9}{1}$ =$\frac{-3}{7}$ . $\frac{1}{-9}$ =$\frac{-3}{7.1}$.$\frac{1}{-3.3}$ = $\frac{7}{3}$