Đáp án:
$\dfrac{1}{3}$ $.$ $\dfrac{5}{7}$ $-$ $\dfrac{7}{27}$ $.$ $\dfrac{36}{14}$
$=$ $\dfrac{5}{21}$ $-$ $\dfrac{252}{378}$
$=$ $\dfrac{5}{21}$ $-$ $\dfrac{2}{3}$
$=$ $\dfrac{5}{21}$ $-$ $\dfrac{14}{21}$
$=$ $\dfrac{-9}{21}$
$=$ $\dfrac{-3}{7}$
BẠN THAM KHẢO NHA!!!