$$-2+(\frac{11}{24}+\frac{5}{6}):1\frac{15}{16}-\frac{2}{5} = -2+(\frac{11}{24}+\frac{20}{24}):\frac{31}{16}-\frac{2}{5} = -2 + (\frac{31}{24} * \frac{16}{31}) - \frac{2}{5} = -2 + \frac{2}{3} - \frac{2}{5} = -2 + \frac{10}{15} - \frac{6}{15} = -2 + \frac{4}{15} = -\frac{30}{15} + \frac{4}{15} = -\frac{26}{15}$$
Ответ: **$$-\frac{26}{15}$$**