r) (1/2)³⋅(3 1/3-2 8/9)²;

г) Выполним действия по порядку.

1. $$3\frac{1}{3} = \frac{3 \cdot 3 + 1}{3} = \frac{9+1}{3} = \frac{10}{3}$$
2. $$2\frac{8}{9} = \frac{2 \cdot 9 + 8}{9} = \frac{18+8}{9} = \frac{26}{9}$$
3. $$\frac{10}{3} - \frac{26}{9} = \frac{10 \cdot 3}{3 \cdot 3} - \frac{26}{9} = \frac{30}{9} - \frac{26}{9} = \frac{30-26}{9} = \frac{4}{9}$$
4. $$(\frac{4}{9})^2 = \frac{4^2}{9^2} = \frac{16}{81}$$
5. $$(\frac{1}{2})^3 = \frac{1^3}{2^3} = \frac{1}{8}$$
6. $$\frac{1}{8} \cdot \frac{16}{81} = \frac{1 \cdot 16}{8 \cdot 81} = \frac{1 \cdot 2}{1 \cdot 81} = \frac{2}{81}$$

Ответ: $$\frac{2}{81}$$