\(\left(-\dfrac{2}{3}\right):\left(-\dfrac{5}{6}\right)+\dfrac{2}{3}:\left(-\dfrac{5}{6}\right)\)
= \(\left[\left(-\dfrac{2}{3}\right):\dfrac{2}{3}\right]+\left[\left(-\dfrac{5}{6}\right):\left(-\dfrac{5}{6}\right)\right]\)
= \(\left(-1\right)+1\)
= \(0\)