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

1. \(\frac{2}{5}+\frac{2}{10}=\frac{4}{10}+\frac{2}{10}=\frac{6}{10}=\frac{3}{5}\).
2. \(\frac{6}{8}-\frac{1}{4}=\frac{3}{4}-\frac{1}{4}=\frac{1}{2}\).
3. \(\frac{17}{25}-\frac{2}{10}=\frac{17}{25}-\frac{1}{5}=\frac{17}{25}-\frac{5}{25}=\frac{12}{25}\).
4. \(\frac{7}{12}+\frac{5}{18}=\frac{21}{36}+\frac{10}{36}=\frac{31}{36}\).
5. \(\frac{3}{4}\cdot\frac{5}{6}=\frac{15}{24}=\frac{5}{8}\).
6. \(\frac{2}{5}:\frac{1}{2}=\frac{2}{5}\cdot2=\frac{4}{5}\).
7. \(\frac{9}{20}:\frac{3}{4}=\frac{9}{20}\cdot\frac{4}{3}=\frac{3}{5}\).
8. \(\frac{14}{25}:\frac{7}{10}=\frac{14}{25}\cdot\frac{10}{7}=\frac{4}{5}\).

Ответ: 1) 3/5; 2) 1/2; 6) 12/25; 7) 31/36; 11) 5/8; 12) 4/5; 16) 3/5; 17) 4/5.