1. Multiply the fractions and mixed numbers: 21. Calculate $\frac{2}{3} \times 3 \times \frac{1}{8}$. Simplify: $3$ as $\frac{3}{1}$. Multiply numerators: $2 \times 3 \times 1 = 6$. Multiply denominators: $3 \times 1 \times 8 = 24$. Result: $\frac{6}{24} = \frac{1}{4}$ after simplification. 22. Calculate $\frac{1}{2} \times 4 \times \frac{4}{5}$. 4 as $\frac{4}{1}$. Multiply numerators: $1 \times 4 \times 4 = 16$. Multiply denominators: $2 \times 1 \times 5 = 10$. Result: $\frac{16}{10} = \frac{8}{5} = 1 \frac{3}{5}$. 23. Calculate $1 \frac{1}{7} \times 2 \frac{1}{2} \times 1 \frac{7}{8}$. Convert to improper fractions: $1 \frac{1}{7} = \frac{8}{7}$, $2 \frac{1}{2} = \frac{5}{2}$, $1 \frac{7}{8} = \frac{15}{8}$. Multiply numerators: $8 \times 5 \times 15 = 600$. Multiply denominators: $7 \times 2 \times 8 = 112$. Result: $\frac{600}{112} = \frac{75}{14} = 5 \frac{5}{14}$. 24. Calculate $7 \times 3 \frac{2}{3} \times 1 \frac{1}{4}$. Convert mixed numbers: $3 \frac{2}{3} = \frac{11}{3}$, $1 \frac{1}{4} = \frac{5}{4}$. Express 7 as $\frac{7}{1}$. Multiply numerators: $7 \times 11 \times 5 = 385$. Multiply denominators: $1 \times 3 \times 4 = 12$. Result: $\frac{385}{12} = 32 \frac{1}{12}$. 2. Write the reciprocals: 25. Reciprocal of $\frac{3}{4}$ is $\frac{4}{3}$. 26. Reciprocal of $\frac{3}{2}$ is $\frac{2}{3}$. 27. Reciprocal of $\frac{2}{7}$ is $\frac{7}{2}$. 28. Reciprocal of $2 \frac{1}{6} = \frac{13}{6}$ is $\frac{6}{13}$. 29. Reciprocal of $3 \frac{2}{7} = \frac{23}{7}$ is $\frac{7}{23}$. 30. Reciprocal of $4 \frac{1}{4} = \frac{17}{4}$ is $\frac{4}{17}$.