15) $$\frac{11}{18}: (\frac{8}{15} + \frac{4}{9}): (\frac{2}{3} - \frac{1}{6})$$

Решим пример по действиям:

1) $$\frac{8}{15} + \frac{4}{9} = \frac{8 \cdot 3 + 4 \cdot 5}{45} = \frac{24 + 20}{45} = \frac{44}{45}$$

2) $$\frac{2}{3} - \frac{1}{6} = \frac{2 \cdot 2 - 1}{6} = \frac{4 - 1}{6} = \frac{3}{6} = \frac{1}{2}$$

3) $$\frac{11}{18}: \frac{44}{45} = \frac{11}{18} \cdot \frac{45}{44} = \frac{11 \cdot 45}{18 \cdot 44} = \frac{1 \cdot 5}{2 \cdot 4} = \frac{5}{8}$$

4) $$\frac{5}{8}: \frac{1}{2} = \frac{5}{8} \cdot \frac{2}{1} = \frac{5 \cdot 2}{8 \cdot 1} = \frac{10}{8} = \frac{5}{4} = 1\frac{1}{4}$$

Ответ: $$1\frac{1}{4}$$