Cách giải:
$a,[6.(\dfrac{-1}{3})^{3}-3.(\dfrac{-1}{3})]:(\dfrac{-1}{3}-1)$
$=[6.\dfrac{-1}{27}+1]:\dfrac{-4}{3}$
$=\dfrac{7}{9}:\dfrac{-4}{3}$
$=\dfrac{-7}{12}$
$b,(\dfrac{2}{3})^{3}.(\dfrac{-3}{4})^{2}.\dfrac{(-1)^{2003}}{(\dfrac{2}{5})^{2}.(\dfrac{-5}{12})^{3}}$
$=\dfrac{8}{27}.\dfrac{9}{16}.\dfrac{1}{(\dfrac{2}{5}.\dfrac{5}{2})^{2}.\dfrac{5}{12}}$
$=\dfrac{1}{6}.\dfrac{1}{\dfrac{5}{12}}$
$=\dfrac{1}{6}.\dfrac{12}{5}$
$=\dfrac{2}{5}$