~ Bạn tham khảo ~
$\dfrac{\bigg(\dfrac3{10}-\dfrac4{15}-\dfrac7{20}\bigg)\cdot\dfrac5{19}}{\bigg(\dfrac1{14}+\dfrac17-\dfrac{-3}{35}\bigg)\cdot\dfrac{-4}3}$
$=\dfrac{\bigg(\dfrac{18}{60}-\dfrac{16}{60}-\dfrac{21}{60}\bigg)\cdot\dfrac5{19}}{\bigg(\dfrac5{70}+\dfrac{10}{70}+\dfrac{6}{70}\bigg)\cdot\dfrac{-4}3}$
$=\dfrac{\dfrac{-19}{60}\cdot\dfrac5{19}}{\dfrac{21}{70}\cdot\dfrac{-4}3}$
$=\dfrac{\dfrac{-1}{12}}{\dfrac{-4}{10}}$
$=\dfrac5{24}$
