1. Выполните действия: a) \(\frac{3}{5} + \frac{1}{5}\); б) \(\frac{5}{18} + \frac{7}{18}\); в) \(\frac{18}{23} + \frac{6}{23}\); г) \(\frac{2}{9} + \frac{4}{9}\); д) \(\frac{17}{20} - \frac{3}{20}\); е) \(\frac{51}{100} - \frac{9}{100}\); ж) \(\frac{11}{45} - \frac{2}{45}\); з) \(\frac{11}{25} - \frac{9}{25} + \frac{2}{25}\).

Решаем примеры на сложение и вычитание дробей с одинаковыми знаменателями.

а) \(\frac{3}{5} + \frac{1}{5} = \frac{3+1}{5} = \frac{4}{5}\)

б) \(\frac{5}{18} + \frac{7}{18} = \frac{5+7}{18} = \frac{12}{18} = \frac{6 \cdot 2}{6 \cdot 3} = \frac{2}{3}\)

в) \(\frac{18}{23} + \frac{6}{23} = \frac{18+6}{23} = \frac{24}{23}\)

г) \(\frac{2}{9} + \frac{4}{9} = \frac{2+4}{9} = \frac{6}{9} = \frac{3 \cdot 2}{3 \cdot 3} = \frac{2}{3}\)

д) \(\frac{17}{20} - \frac{3}{20} = \frac{17-3}{20} = \frac{14}{20} = \frac{2 \cdot 7}{2 \cdot 10} = \frac{7}{10}\)

е) \(\frac{51}{100} - \frac{9}{100} = \frac{51-9}{100} = \frac{42}{100} = \frac{2 \cdot 21}{2 \cdot 50} = \frac{21}{50}\)

ж) \(\frac{11}{45} - \frac{2}{45} = \frac{11-2}{45} = \frac{9}{45} = \frac{9 \cdot 1}{9 \cdot 5} = \frac{1}{5}\)

з) \(\frac{11}{25} - \frac{9}{25} + \frac{2}{25} = \frac{11-9+2}{25} = \frac{4}{25}\)

Ответ: а) \(\frac{4}{5}\); б) \(\frac{2}{3}\); в) \(\frac{24}{23}\); г) \(\frac{2}{3}\); д) \(\frac{7}{10}\); е) \(\frac{21}{50}\); ж) \(\frac{1}{5}\); з) \(\frac{4}{25}\).