1) 2/5 : 7/35 = 2/7 * 14/15 2) 7/10 : 3/14 = 3/9 3) 1/7 : 1/8 4) 2/13 : 1/3 7) 4/33 : 121/42 = 55/3 8) 7/9 : 2/3 9) 5/6 : 8/9 10) 8/9 : 2/3 11) 1/7 : 4/11 15) 2/4 : 3/5 16) 8/2 : 9/5 17) 1/3 : 2/3 18) 1/16 : 1/7

Решение:

1. \( \frac{2}{5} \div \frac{7}{35} = \frac{2}{5} \times \frac{35}{7} = \frac{2 \times 35}{5 \times 7} = \frac{70}{35} = 2 \)
2. \( \frac{7}{10} \div \frac{3}{14} = \frac{7}{10} \times \frac{14}{3} = \frac{7 \times 14}{10 \times 3} = \frac{98}{30} = \frac{49}{15} \)
3. \( \frac{1}{7} \div \frac{1}{8} = \frac{1}{7} \times \frac{8}{1} = \frac{1 \times 8}{7 \times 1} = \frac{8}{7} \)
4. \( \frac{2}{13} \div \frac{1}{3} = \frac{2}{13} \times \frac{3}{1} = \frac{2 \times 3}{13 \times 1} = \frac{6}{13} \)
5. \( \frac{4}{33} \div \frac{121}{42} = \frac{4}{33} \times \frac{42}{121} = \frac{4 \times 42}{33 \times 121} = \frac{168}{3993} = \frac{56}{1331} \)
6. \( \frac{7}{9} \div \frac{2}{3} = \frac{7}{9} \times \frac{3}{2} = \frac{7 \times 3}{9 \times 2} = \frac{21}{18} = \frac{7}{6} \)
7. \( \frac{5}{6} \div \frac{8}{9} = \frac{5}{6} \times \frac{9}{8} = \frac{5 \times 9}{6 \times 8} = \frac{45}{48} = \frac{15}{16} \)
8. \( \frac{8}{9} \div \frac{2}{3} = \frac{8}{9} \times \frac{3}{2} = \frac{8 \times 3}{9 \times 2} = \frac{24}{18} = \frac{4}{3} \)
9. \( \frac{1}{7} \div \frac{4}{11} = \frac{1}{7} \times \frac{11}{4} = \frac{1 \times 11}{7 \times 4} = \frac{11}{28} \)
10. \( \frac{2}{4} \div \frac{3}{5} = \frac{1}{2} \times \frac{5}{3} = \frac{1 \times 5}{2 \times 3} = \frac{5}{6} \)
11. \( \frac{8}{2} \div \frac{9}{5} = 4 \div \frac{9}{5} = 4 \times \frac{5}{9} = \frac{4 \times 5}{9} = \frac{20}{9} \)
12. \( \frac{1}{3} \div \frac{2}{3} = \frac{1}{3} \times \frac{3}{2} = \frac{1 \times 3}{3 \times 2} = \frac{3}{6} = \frac{1}{2} \)
13. \( \frac{1}{16} \div \frac{1}{7} = \frac{1}{16} \times \frac{7}{1} = \frac{1 \times 7}{16 \times 1} = \frac{7}{16} \)

Ответ: 1) 2; 2) 49/15; 3) 8/7; 4) 6/13; 7) 56/1331; 8) 7/6; 9) 15/16; 10) 4/3; 11) 11/28; 15) 5/6; 16) 20/9; 17) 1/2; 18) 7/16.