Đáp án:
$\text{ A = $\dfrac{2}{5}$ + ($\dfrac{-4}{3}$) + ( $\dfrac{-1}{2}$) }$
$\text{ = $\dfrac{12}{30}$ + ( $\dfrac{-40}{30}$) + ($\dfrac{-15}{30}$ ) }$
$\text{ = $\dfrac{-43}{30}$ }$
$\text{B = $\dfrac{1}{3}$ - [ ($\dfrac{-5}{4}$) - ($\dfrac{1}{4}$ + $\dfrac{3}{8}$) ] }$
$\text{ = $\dfrac{1}{3}$ - [ $\dfrac{-5}{4}$ - $\dfrac{5}{8}$ ] }$
$\text{ = $\dfrac{1}{3}$ - ($\dfrac{-15}{8}$) }$
$\text{ = $\dfrac{1}{3}$ + $\dfrac{15}{8}$ }$
$\text{ = $\dfrac{53}{24}$ }$
