Задание 2. Вычислите: 1) 2/5 + 2/10; 2) 6/8 − 1/4; 3) 1/3 + 2/6; 4) 4/7 + 3/14; 5) 9/12 − 1/6; 6) 17/25 − 2/10; 7) 7/12 + 5/18; 8) 9/14 − 2/21; 9) 11/15 + 7/45; 10) 19/24 + 5/16; 11) 3/4 · 5/6; 12) 2/5 : 1/2; 13) 5/8 : 1/4; 14) 8/15 · 3/10; 15) 15/16 · 8/15; 16) 9/20 : 3/4; 17) 14/25 : 7/10; 18) 17/20 : 5/12; 19) 24/35 : 8/21; 20) 18/25 : 6/11.

1. \(\frac{2}{5}+\frac{2}{10}=\frac{2}{5}+\frac{1}{5}=\frac{3}{5}\)
2. \(\frac{6}{8}-\frac{1}{4}=\frac{3}{4}-\frac{1}{4}=\frac{1}{2}\)
3. \(\frac{1}{3}+\frac{2}{6}=\frac{1}{3}+\frac{1}{3}=\frac{2}{3}\)
4. \(\frac{4}{7}+\frac{3}{14}=\frac{8}{14}+\frac{3}{14}=\frac{11}{14}\)
5. \(\frac{9}{12}-\frac{1}{6}=\frac{3}{4}-\frac{1}{6}=\frac{7}{12}\)
6. \(\frac{17}{25}-\frac{2}{10}=\frac{17}{25}-\frac{1}{5}=\frac{12}{25}\)
7. \(\frac{7}{12}+\frac{5}{18}=\frac{21}{36}+\frac{10}{36}=\frac{31}{36}\)
8. \(\frac{9}{14}-\frac{2}{21}=\frac{27}{42}-\frac{4}{42}=\frac{23}{42}\)
9. \(\frac{11}{15}+\frac{7}{45}=\frac{33}{45}+\frac{7}{45}=\frac{8}{9}\)
10. \(\frac{19}{24}+\frac{5}{16}=\frac{38}{48}+\frac{15}{48}=\frac{53}{48}\)
11. \(\frac{3}{4}\cdot\frac{5}{6}=\frac{15}{24}=\frac{5}{8}\)
12. \(\frac{2}{5}:\frac{1}{2}=\frac{2}{5}\cdot2=\frac{4}{5}\)
13. \(\frac{5}{8}:\frac{1}{4}=\frac{5}{8}\cdot4=\frac{5}{2}\)
14. \(\frac{8}{15}\cdot\frac{3}{10}=\frac{24}{150}=\frac{4}{25}\)
15. \(\frac{15}{16}\cdot\frac{8}{15}=\frac{1}{2}\)
16. \(\frac{9}{20}:\frac{3}{4}=\frac{9}{20}\cdot\frac{4}{3}=\frac{3}{5}\)
17. \(\frac{14}{25}:\frac{7}{10}=\frac{14}{25}\cdot\frac{10}{7}=\frac{4}{5}\)
18. \(\frac{17}{20}:\frac{5}{12}=\frac{17}{20}\cdot\frac{12}{5}=\frac{51}{25}\)
19. \(\frac{24}{35}:\frac{8}{21}=\frac{24}{35}\cdot\frac{21}{8}=\frac{9}{5}\)
20. \(\frac{18}{25}:\frac{6}{11}=\frac{18}{25}\cdot\frac{11}{6}=\frac{33}{25}\)

Ответ: 1) 3/5; 2) 1/2; 3) 2/3; 4) 11/14; 5) 7/12; 6) 12/25; 7) 31/36; 8) 23/42; 9) 8/9; 10) 53/48; 11) 5/8; 12) 4/5; 13) 5/2; 14) 4/25; 15) 1/2; 16) 3/5; 17) 4/5; 18) 51/25; 19) 9/5; 20) 33/25.