a) $\frac{1}{2}$ x - $\frac{2}{5}$ = $\frac{-4}{5}$
=> $\frac{1}{2}$ x = $\frac{-4}{5}$ + $\frac{2}{5}$
=> $\frac{1}{2}$ x = $\frac{-2}{5}$
=> x = $\frac{-2}{5}$ : $\frac{1}{2}$
=> x = $\frac{-2}{5}$ . 2
=> x = $\frac{-4}{5}$
Vậy x = $\frac{-4}{5}$
b) 5$\frac{4}{7}$ : x = 13
=> x = 5$\frac{4}{7}$ : 13
=> x = $\frac{39}{7}$ . $\frac{1}{13}$
=> x = $\frac{3}{7}$
Vậy x = $\frac{3}{7}$
