Đáp án:
$\dfrac{-21}{22}$ .$\dfrac{4}{11}$ +$\dfrac{-21}{22}$ .$\dfrac{7}{11}$ -/$\dfrac{-21}{22}$ /
=$\dfrac{-21}{22}$ .$\dfrac{4}{11}$ +$\dfrac{-21}{22}$ .$\dfrac{7}{11}$ -$\dfrac{21}{22}$
=$\dfrac{-21}{22}$ .$\dfrac{4}{11}$ +$\dfrac{-21}{22}$ .$\dfrac{7}{11}$ +$\dfrac{-21}{22}$ .1
=$\dfrac{-21}{22}$ .($\dfrac{4}{11}$ +$\dfrac{7}{11}$ +$1$)
=$\dfrac{-21}{22}$ .($\dfrac{4}{11}$ +$\dfrac{7}{11}$ +$\dfrac{11}{11}$ )
=$\dfrac{-21}{22}$ .$\dfrac{22}{11}$
=$\dfrac{-21.22}{22.11}$
=$\dfrac{-21}{11}$