tính nhanh

\(b.B=\dfrac{1}{3}.\dfrac{-6}{13}.\dfrac{-9}{10}.\dfrac{-13}{36}\)

\(\dfrac{2}{3}.\dfrac{-5}{7}\)

\(\dfrac{-1}{3}.\dfrac{5}{9}\)

\(\dfrac{-2}{5}.\dfrac{10}{4}\)

\(\dfrac{-3}{7}.\dfrac{5}{15}\)

\(\dfrac{-7}{3}.\dfrac{9}{21}\)

\(\dfrac{5}{7}-x=\dfrac{9}{21}\)

\(-x-\dfrac{1}{3}=\dfrac{2}{6}\)

\(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)

Tìm x biết :

\(x+\dfrac{1}{2}=\dfrac{33}{4}\)

\(\dfrac{5}{6}-x=\dfrac{1}{3}\)

\(x+\dfrac{4}{5}=\dfrac{-2}{3}\)