2. Найти значение выражения:

Решение:

1. \( \frac{9}{10} + \frac{2}{5} = \frac{9}{10} + \frac{4}{10} = \frac{13}{10} = 1 \frac{3}{10} \)
2. \( \frac{11}{20} - \frac{1}{4} = \frac{11}{20} - \frac{5}{20} = \frac{6}{20} = \frac{3}{10} \)
3. \( \frac{3}{5} + \frac{1}{2} = \frac{6}{10} + \frac{5}{10} = \frac{11}{10} = 1 \frac{1}{10} \)
4. \( \frac{36}{50} - \frac{3}{25} = \frac{36}{50} - \frac{6}{50} = \frac{30}{50} = \frac{3}{5} \)
5. \( \frac{8}{10} + \frac{1}{5} = \frac{8}{10} + \frac{2}{10} = \frac{10}{10} = 1 \)
6. \( \frac{12}{30} - \frac{3}{50} = \frac{60}{150} - \frac{9}{150} = \frac{51}{150} = \frac{17}{50} \)
7. \( \frac{3}{4} + \frac{3}{12} = \frac{9}{12} + \frac{3}{12} = \frac{12}{12} = 1 \)

Ответ: 1. \( 1 \frac{3}{10} \), 2. \( \frac{3}{10} \), 3. \( 1 \frac{1}{10} \), 4. \( \frac{3}{5} \), 5. \( 1 \), 6. \( \frac{17}{50} \), 7. \( 1 \).