What number should be subtracted from $$\dfrac {-2}{3}$$ to get $$\dfrac {-1}{6}$$?
Let us consider $$x$$
$$\dfrac {-2}{3} - x = \dfrac {-1}{6}$$
Solving for $$x$$,
$$x = \dfrac {-2}{3} - \dfrac {-1}{6}$$
By taking LCM of $$3$$ and $$6$$ is $$6$$
$$\dfrac {(-2\times 2) - (-1\times 1)}{6} = \dfrac {-4 - (-1)}{6} = \dfrac {-4 + 1}{6} = \dfrac {-3}{6}$$ we further can divide to lowest terms, $$\dfrac {-3\div 3}{6\div 3} = \dfrac {-1}{2}$$
$$x = \dfrac {-1}{2} \therefore \dfrac {-1}{2}$$ should be subtracted from $$\dfrac {-2}{3}$$ to get $$\dfrac {-1}{6}$$.