Giải thích các bước giải:
a.$\dfrac{-5}9+\dfrac4{11}+\dfrac7{11}$
$=\dfrac{-5}9+(\dfrac4{11}+\dfrac7{11})$
$=\dfrac{-5}9+\dfrac{4+7}{11}$
$=\dfrac{-5}9+\dfrac{11}{11}$
$=-\dfrac{5}9+1$
$=1-\dfrac59$
$=\dfrac49$
b.$\dfrac{-2}{5}+\dfrac38+\dfrac{-3}5+\dfrac{13}8$
$=(\dfrac38+\dfrac{13}8)+(\dfrac{-2}{5}+\dfrac{-3}5)$
$=\dfrac{3+13}{8}+\dfrac{-2-3}{5}$
$=\dfrac{16}8+\dfrac{-5}5$
$=2-1$
$=1$