9 вариант: 1) 13/20 − 2/5; 2) 12 − 2 67/100; 3) 5 7/12 + 3 1/4; 4) 24 3/10 − 4 3/5; 5) 1/12 × 4; 6) 3/8 × 2 2/3; 7) 14/39 : 7/13; 8) 7 1/3 : 1 2/9.

1. Приведём к общему знаменателю: \(\frac{13}{20}-\frac{2}{5}=\frac{13}{20}-\frac{8}{20}=\frac{5}{20}=\frac{1}{4}\).
2. \(12-2\frac{67}{100}=11\frac{100}{100}-2\frac{67}{100}=9\frac{33}{100}\).
3. \(5\frac{7}{12}+3\frac{1}{4}=8+\frac{7}{12}+\frac{3}{12}=8\frac{10}{12}=8\frac{5}{6}\).
4. \(24\frac{3}{10}-4\frac{3}{5}=24\frac{3}{10}-4\frac{6}{10}=19\frac{7}{10}\).
5. \(\frac{1}{12}\times4=\frac{4}{12}=\frac{1}{3}\).
6. \(\frac{3}{8}\times2\frac{2}{3}=\frac{3}{8}\times\frac{8}{3}=1\).
7. \(\frac{14}{39}:\frac{7}{13}=\frac{14}{39}\times\frac{13}{7}=\frac{2}{3}\).
8. \(7\frac{1}{3}:1\frac{2}{9}=\frac{22}{3}:\frac{11}{9}=\frac{22}{3}\times\frac{9}{11}=6\).

Ответ: 1) 1/4; 2) 9 33/100; 3) 8 5/6; 4) 19 7/10; 5) 1/3; 6) 1; 7) 2/3; 8) 6.