\(\left(\dfrac{5}{3}-1\right)^7:\left(\dfrac{8}{27}\right)^5\)
\(=\left(\dfrac{2}{3}\right)^7:\left(\dfrac{2^3}{3^3}\right)^5\)
\(=\left(\dfrac{2}{3}\right)^7:\left(\dfrac{2}{3}\right)^{15}\)
\(=\left(\dfrac{2}{3}\right)^{7-15}\)
\(=\left(\dfrac{2}{3}\right)^{-8}\)