$\begin{array}{l}
\sqrt {\dfrac{{16}}{{49}}} + {\left( { - 0,5} \right)^3} - \left| { - \dfrac{4}{7}} \right| - \dfrac{7}{8}\\
= \sqrt {{{\left( {\dfrac{4}{7}} \right)}^2}} + {\left( { - \dfrac{1}{2}} \right)^3} - \dfrac{4}{7} - \dfrac{7}{8}\\
= \dfrac{4}{7} + \left( { - \dfrac{1}{8}} \right) - \dfrac{4}{7} - \dfrac{7}{8}\\
= \dfrac{4}{7} - \dfrac{1}{8} - \dfrac{4}{7} - \dfrac{7}{8}\\
= \left( {\dfrac{4}{7} - \dfrac{4}{7}} \right) - \dfrac{1}{8} - \dfrac{7}{8}\\
= 0 - \dfrac{8}{8} = - 1
\end{array}$
