Решение:
1. $$1 \frac{8}{17} = \frac{1 \cdot 17 + 8}{17} = \frac{25}{17}$$
2. $$2 \frac{7}{11} = \frac{2 \cdot 11 + 7}{11} = \frac{29}{11}$$
3. $$\frac{12}{17} + \frac{29}{11} = \frac{12 \cdot 11}{17 \cdot 11} + \frac{29 \cdot 17}{11 \cdot 17} = \frac{132}{187} + \frac{493}{187} = \frac{625}{187}$$
4. $$\frac{25}{17} : \frac{625}{187} = \frac{25}{17} \cdot \frac{187}{625} = \frac{1}{1} \cdot \frac{11}{25} = \frac{11}{25} = 0.44$$
Ответ: 0.44