2) $$(1 \frac{9}{16} \cdot 3 \frac{1}{5} + 1 \frac{2}{3} - 9 \div 2 \frac{2}{5}) \div (17 \frac{7}{12} - 6 \frac{1}{3}) =$$

Решим пример по действиям:

1) $$1 \frac{9}{16} \cdot 3 \frac{1}{5} = \frac{25}{16} \cdot \frac{16}{5} = \frac{25 \cdot 16}{16 \cdot 5} = \frac{25}{5} = 5$$

2) $$2 \frac{2}{5} = \frac{12}{5}$$

3) $$9 \div 2 \frac{2}{5} = 9 \div \frac{12}{5} = 9 \cdot \frac{5}{12} = \frac{9 \cdot 5}{12} = \frac{3 \cdot 3 \cdot 5}{3 \cdot 4} = \frac{15}{4} = 3 \frac{3}{4}$$

4) $$1 \frac{2}{3} = \frac{5}{3}$$

5) $$5 + 1 \frac{2}{3} - 9 \div 2 \frac{2}{5} = 5 + \frac{5}{3} - 3 \frac{3}{4} = 5 + \frac{5}{3} - \frac{15}{4} = \frac{5 \cdot 12}{12} + \frac{5 \cdot 4}{3 \cdot 4} - \frac{15 \cdot 3}{4 \cdot 3} = \frac{60}{12} + \frac{20}{12} - \frac{45}{12} = \frac{60 + 20 - 45}{12} = \frac{35}{12} = 2 \frac{11}{12}$$

6) $$17 \frac{7}{12} - 6 \frac{1}{3} = 17 \frac{7}{12} - 6 \frac{4}{12} = (17 - 6) + (\frac{7}{12} - \frac{4}{12}) = 11 \frac{3}{12} = 11 \frac{1}{4}$$

7) $$2 \frac{11}{12} \div 11 \frac{1}{4} = \frac{35}{12} \div \frac{45}{4} = \frac{35}{12} \cdot \frac{4}{45} = \frac{35 \cdot 4}{12 \cdot 45} = \frac{35 \cdot 4}{4 \cdot 3 \cdot 5 \cdot 9} = \frac{7}{3 \cdot 9} = \frac{7}{27}$$

Ответ: $$\frac{7}{27}$$