Давай решим эти примеры по порядку.
A) 5$$\frac{5}{7}\cdot1\frac{1}{20}$$
5$$\frac{5}{7}$$ = $$\frac{5 \times 7 + 5}{7}$$ = $$\frac{35 + 5}{7}$$ = $$\frac{40}{7}$$
1$$\frac{1}{20}$$ = $$\frac{1 \times 20 + 1}{20}$$ = $$\frac{20 + 1}{20}$$ = $$\frac{21}{20}$$
$$\frac{40}{7} \cdot \frac{21}{20}$$ = $$\frac{40 \times 21}{7 \times 20}$$ = $$\frac{840}{140}$$
$$\frac{840}{140}$$ = $$\frac{84}{14}$$ = 6
Б) 6$$\frac{2}{3}\cdot2\frac{1}{10}$$
6$$\frac{2}{3}$$ = $$\frac{6 \times 3 + 2}{3}$$ = $$\frac{18 + 2}{3}$$ = $$\frac{20}{3}$$
2$$\frac{1}{10}$$ = $$\frac{2 \times 10 + 1}{10}$$ = $$\frac{20 + 1}{10}$$ = $$\frac{21}{10}$$
$$\frac{20}{3} \cdot \frac{21}{10}$$ = $$\frac{20 \times 21}{3 \times 10}$$ = $$\frac{420}{30}$$
$$\frac{420}{30}$$ = $$\frac{42}{3}$$ = 14
B) 7$$\frac{1}{5}\cdot2\frac{2}{5}$$
7$$\frac{1}{5}$$ = $$\frac{7 \times 5 + 1}{5}$$ = $$\frac{35 + 1}{5}$$ = $$\frac{36}{5}$$
2$$\frac{2}{5}$$ = $$\frac{2 \times 5 + 2}{5}$$ = $$\frac{10 + 2}{5}$$ = $$\frac{12}{5}$$
$$\frac{36}{5} \cdot \frac{12}{5}$$ = $$\frac{36 \times 12}{5 \times 5}$$ = $$\frac{432}{25}$$
$$\frac{432}{25}$$ = 17$$\frac{7}{25}$$
Г) 8$$\frac{1}{3}\cdot2\frac{7}{9}$$
8$$\frac{1}{3}$$ = $$\frac{8 \times 3 + 1}{3}$$ = $$\frac{24 + 1}{3}$$ = $$\frac{25}{3}$$
2$$\frac{7}{9}$$ = $$\frac{2 \times 9 + 7}{9}$$ = $$\frac{18 + 7}{9}$$ = $$\frac{25}{9}$$
$$\frac{25}{3} \cdot \frac{25}{9}$$ = $$\frac{25 \times 25}{3 \times 9}$$ = $$\frac{625}{27}$$
$$\frac{625}{27}$$ = 23$$\frac{4}{27}$$
Ответ: А) 6; Б) 14; В) 17$$\frac{7}{25}$$; Г) 23$$\frac{4}{27}$$
Отличная работа! Ты хорошо справляешься с математикой. Продолжай в том же духе, и у тебя все получится!