Đáp án:$ \dfrac{42}{4}$
Giải thích các bước giải:
$\left ( \dfrac{1+\dfrac{1}{5}}{1-\dfrac{1}{5}} \right ):\left ( \dfrac{1-\dfrac{3}{4}}{1+\dfrac{3}{4}} \right )$
$= \dfrac{\dfrac{6}{5}}{\dfrac{4}{5}}:\dfrac{\dfrac{1}{4}}{\dfrac{7}{4}}$
$= \dfrac{6}{4}:\dfrac{1}{7}$
$= \dfrac{42}{4}$