Laske.

a) [[$ \dfrac{1}{2} + \dfrac{1}{6} $]] =

b) [[$ \dfrac{3}{20} + \dfrac{1}{4} $]] =

c) [[$ \dfrac{5}{6} - \dfrac{1}{3} $]] =

d) [[$ \dfrac{1}{4} - \dfrac{1}{8} $]] =