\[\left( \frac{7}{16} - \left( - \frac{5}{24} \right) \right)\ :\left( - 1\frac{15}{16} \right) =\]
\[= \left( \frac{21}{48} + \frac{10}{48} \right)\ :\left( - \frac{31}{16} \right) =\]
\[= \frac{31}{48} \cdot \left( - \frac{16}{31} \right) =\]
\[= - \frac{16}{48} = - \frac{1}{3}\]