Tính: $\dfrac{5}{7} - \dfrac{2}{5}$

$\dfrac{9}{4}$          

$\dfrac{4}{9}$ 

$\dfrac{{ - 4}}{9}$

Tất cả các đáp án trên đều đúng

$\dfrac{3}{7};\dfrac{7}{3}$ 

$\dfrac{{11}}{{15}};\dfrac{{ - 11}}{{15}}$  

$5; - \dfrac{1}{5}$

$\dfrac{8}{9};\dfrac{9}{8}$

$\dfrac{{-14}}{{56}}$ 

$\dfrac{{ - 15}}{{56}}$  

$\dfrac{-21}{{56}}$

$\dfrac{{ 15}}{{56}}$

$\dfrac{{27}}{{17}}$  

$\dfrac{{45}}{{17}}$           

$\dfrac{{24}}{{27}}$

$\dfrac{{-45}}{{17}}$

$\dfrac{{ - 2}}{{15}}$

$\dfrac{{ - 2}}{{25}}$  

$\dfrac{{ - 3}}{{15}}$

$\dfrac{3}{{25}}$

$- \dfrac{1}{{15}}$ 

$\dfrac{1}{6}$  

$\dfrac{1}{{15}}$

$\dfrac{1}{{10}}$

$\dfrac{4}{{21}}$ 

$\dfrac{{ - 1}}{{42}}$  

$\dfrac{1}{6}$

$- \dfrac{4}{{21}}$