Решение:

Первый столбец:

1. $$\frac{4}{7} \cdot \frac{8}{21} = \frac{4 \cdot 8}{7 \cdot 21} = \frac{32}{147} = \square$$
2. $$\frac{32}{147} \cdot \frac{14}{15} = \frac{32 \cdot 14}{147 \cdot 15} = \frac{32 \cdot 2}{21 \cdot 15} = \frac{64}{315} = \bigcirc$$
3. $$\frac{64}{315} + 2\frac{1}{3} = \frac{64}{315} + \frac{7}{3} = \frac{64}{315} + \frac{7 \cdot 105}{3 \cdot 105} = \frac{64}{315} + \frac{735}{315} = \frac{799}{315} = 2\frac{169}{315} = \triangle$$
4. $$2\frac{169}{315} - 1\frac{4}{5} = 2\frac{169}{315} - 1\frac{4 \cdot 63}{5 \cdot 63} = 2\frac{169}{315} - 1\frac{252}{315} = \frac{799}{315} - \frac{315 + 252}{315} = \frac{799}{315} - \frac{567}{315} = \frac{232}{315} = \star$$

Второй столбец:

1. $$\frac{7}{27} : \frac{1}{9} = \frac{7}{27} \cdot \frac{9}{1} = \frac{7 \cdot 9}{27 \cdot 1} = \frac{7 \cdot 1}{3 \cdot 1} = \frac{7}{3} = 2\frac{1}{3} = \square$$
2. $$2\frac{1}{3} \cdot \frac{51}{56} = \frac{7}{3} \cdot \frac{51}{56} = \frac{7 \cdot 51}{3 \cdot 56} = \frac{1 \cdot 17}{1 \cdot 8} = \frac{17}{8} = 2\frac{1}{8} = \bigcirc$$
3. $$2\frac{1}{8} + 2\frac{1}{6} = \frac{17}{8} + \frac{13}{6} = \frac{17 \cdot 3}{8 \cdot 3} + \frac{13 \cdot 4}{6 \cdot 4} = \frac{51}{24} + \frac{52}{24} = \frac{103}{24} = 4\frac{7}{24} = \triangle$$
4. $$4\frac{7}{24} - 1\frac{1}{3} = 4\frac{7}{24} - 1\frac{1 \cdot 8}{3 \cdot 8} = 4\frac{7}{24} - 1\frac{8}{24} = 3\frac{31}{24} - 1\frac{8}{24} = 2\frac{23}{24} = \star$$

Ответ:

Первый столбец:

• $$\square = \frac{32}{147}$$
• $$\bigcirc = \frac{64}{315}$$
• $$\triangle = 2\frac{169}{315}$$
• $$\star = \frac{232}{315}$$

Второй столбец:

• $$\square = 2\frac{1}{3}$$
• $$\bigcirc = 2\frac{1}{8}$$
• $$\triangle = 4\frac{7}{24}$$
• $$\star = 2\frac{23}{24}$$