8)15号-4층)2号一步。

Решение:

в) $$(5 \frac{1}{5} - 4 \frac{7}{10}) \cdot 2 \frac{2}{3} = $$

1. $$5 \frac{1}{5} = \frac{5 \cdot 5 + 1}{5} = \frac{25 + 1}{5} = \frac{26}{5}$$
2. $$4 \frac{7}{10} = \frac{4 \cdot 10 + 7}{10} = \frac{40 + 7}{10} = \frac{47}{10}$$
3. $$\frac{26}{5} - \frac{47}{10} = \frac{26 \cdot 2}{5 \cdot 2} - \frac{47}{10} = \frac{52}{10} - \frac{47}{10} = \frac{52 - 47}{10} = \frac{5}{10} = \frac{1}{2}$$
4. $$2 \frac{2}{3} = \frac{2 \cdot 3 + 2}{3} = \frac{6 + 2}{3} = \frac{8}{3}$$
5. $$\frac{1}{2} \cdot \frac{8}{3} = \frac{1 \cdot 8}{2 \cdot 3} = \frac{8}{6} = \frac{2 \cdot 4}{2 \cdot 3} = \frac{4}{3} = 1 \frac{1}{3}$$

Ответ: $$1 \frac{1}{3}$$