\(a)\left(\dfrac{2}{3}\right)^2.3-\dfrac{2}{9}:\dfrac{2}{3}\)
\(=\dfrac{4}{9}.3-\dfrac{2}{9}:\dfrac{2}{3}\)
\(=\dfrac{4}{3}-\dfrac{1}{3}\)
\(=1\)
\(b)2\dfrac{1}{2}+\dfrac{4}{7}:\left(\dfrac{-8}{7}\right)\)
\(=\dfrac{5}{2}+\dfrac{4}{7}:\left(\dfrac{-8}{7}\right)\)
\(=\dfrac{5}{2}+\dfrac{-1}{2}\)
\(=2\)