$\text{Giải thích các bước giải:}$
$\text{Bài 1:}$
$a, \dfrac{3}{5} - \dfrac{5}{6}$
$= \dfrac{18}{30} - \dfrac{25}{30}$
$= \dfrac{-7}{30}$
$b, \dfrac{13}{30} + \dfrac{-1}{5}$
$= \dfrac{13}{30} + \dfrac{-6}{30}$
$= \dfrac{7}{30}$
$\text{Bài 2:}$
$a, \dfrac{3}{4} - x = 1$
$⇒ x = \dfrac{3}{4} - 1$
$⇒ x = \dfrac{3}{4} - \dfrac{4}{4}$
$⇒ x = \dfrac{-1}{4}$
$b, x - 4 = \dfrac{1}{5}$
$⇒ x = \dfrac{1}{5} + 4$
$⇒ x = \dfrac{1}{5} + \dfrac{20}{5}$
$= \dfrac{21}{5}$
$\text{Chúc bạn học tốt !}$
