Выполните сложение дробей и смешанных чисел: 1) 2/5 + 3/10; 2) 2/5 + 4/7; 3) 2/5 + 1 1/20; 4) 2/5 + 1/2; 5) 2/5 + 3/5; 6) 2/5 + 7/15; 7) 2/5 + 9/10; 8) 2/5 + 3/8; 9) 2/5 + 1 1/5; 10) 2/5 + 2/9; 11) 2/5 + 17/20; 12) 2/5 + 7/10; 13) 2/5 + 2 4/5; 14) 2/5 + 2/3; 15) 2/5 + 6/25.

1. \(\frac{2}{5}+\frac{3}{10}=\frac{4}{10}+\frac{3}{10}=\frac{7}{10}\).
2. \(\frac{2}{5}+\frac{4}{7}=\frac{14}{35}+\frac{20}{35}=\frac{34}{35}\).
3. \(\frac{2}{5}+1\frac{1}{20}=\frac{8}{20}+1\frac{1}{20}=1\frac{9}{20}\).
4. \(\frac{2}{5}+\frac{1}{2}=\frac{4}{10}+\frac{5}{10}=\frac{9}{10}\).
5. \(\frac{2}{5}+\frac{3}{5}=\frac{5}{5}=1\).
6. \(\frac{2}{5}+\frac{7}{15}=\frac{6}{15}+\frac{7}{15}=\frac{13}{15}\).
7. \(\frac{2}{5}+\frac{9}{10}=\frac{4}{10}+\frac{9}{10}=1\frac{3}{10}\).
8. \(\frac{2}{5}+\frac{3}{8}=\frac{16}{40}+\frac{15}{40}=\frac{31}{40}\).
9. \(\frac{2}{5}+1\frac{1}{5}=\frac{2}{5}+1\frac{1}{5}=1\frac{3}{5}\).
10. \(\frac{2}{5}+\frac{2}{9}=\frac{18}{45}+\frac{10}{45}=\frac{28}{45}\).
11. \(\frac{2}{5}+\frac{17}{20}=\frac{8}{20}+\frac{17}{20}=\frac{25}{20}=1\frac{1}{4}\).
12. \(\frac{2}{5}+\frac{7}{10}=\frac{4}{10}+\frac{7}{10}=1\frac{1}{10}\).
13. \(\frac{2}{5}+2\frac{4}{5}=2\frac{6}{5}=3\frac{1}{5}\).
14. \(\frac{2}{5}+\frac{2}{3}=\frac{6}{15}+\frac{10}{15}=\frac{16}{15}=1\frac{1}{15}\).
15. \(\frac{2}{5}+\frac{6}{25}=\frac{10}{25}+\frac{6}{25}=\frac{16}{25}\).

Ответ: 7/10; 34/35; 1 9/20; 9/10; 1; 13/15; 1 3/10; 31/40; 1 3/5; 28/45; 1 1/4; 1 1/10; 3 1/5; 1 1/15; 16/25.