Resposta:

[tex](-\dfrac{2}{3})+(-\dfrac{5}{6})=\\ \\ \\ -\dfrac{2}{3}-\dfrac{5}6}=\\ \\ \\ mmc(3,6)=6\\ \\ \\ \dfrac{-4-5}{6}=-\dfrac{9}{6}=-\dfrac{3}{2}[/tex]