Ответ:

  1. а) \(\frac{1}{4}+0.7-\frac{1}{5}=\frac{1}{4}+\frac{7}{10}-\frac{1}{5}=\frac{5}{20}+\frac{14}{20}-\frac{4}{20}=\frac{15}{20}=\frac{3}{4}\).
  2. б) \(0.8-0.3-\frac{2}{5}=\frac{8}{10}-\frac{3}{10}-\frac{4}{10}=\frac{1}{10}\).
  3. в) \(\frac{4}{5}-\frac{1}{3}+0.6=\frac{4}{5}-\frac{1}{3}+\frac{3}{5}=\frac{21}{15}-\frac{5}{15}=\frac{16}{15}=1\frac{1}{15}\).
  4. г) \(\frac{7}{9}+0.4-0.6=\frac{7}{9}+\frac{4}{10}-\frac{6}{10}=\frac{7}{9}-\frac{1}{5}=\frac{35}{45}-\frac{9}{45}=\frac{26}{45}\).