Вычисление дробей с разными знаменателями

4. Вычислите: 1) \[\frac{22}{27} - \frac{5}{9} = \frac{22}{27} - \frac{5 \cdot 3}{9 \cdot 3} = \frac{22}{27} - \frac{15}{27} = \frac{7}{27}\] 2) \[\frac{4}{5} - \frac{3}{4} = \frac{4 \cdot 4}{5 \cdot 4} - \frac{3 \cdot 5}{4 \cdot 5} = \frac{16}{20} - \frac{15}{20} = \frac{1}{20}\] 3) \[\frac{7}{10} + \frac{1}{4} = \frac{7 \cdot 2}{10 \cdot 2} + \frac{1 \cdot 5}{4 \cdot 5} = \frac{14}{20} + \frac{5}{20} = \frac{19}{20}\] 4) \[\frac{3}{4} - \frac{2}{5} = \frac{3 \cdot 5}{4 \cdot 5} - \frac{2 \cdot 4}{5 \cdot 4} = \frac{15}{20} - \frac{8}{20} = \frac{7}{20}\] 5) \[\frac{4}{7} - \frac{1}{21} = \frac{4 \cdot 3}{7 \cdot 3} - \frac{1}{21} = \frac{12}{21} - \frac{1}{21} = \frac{11}{21}\] 6) \[\frac{3}{20} - \frac{1}{25} = \frac{3 \cdot 5}{20 \cdot 5} - \frac{1 \cdot 4}{25 \cdot 4} = \frac{15}{100} - \frac{4}{100} = \frac{11}{100}\] 7) \[\frac{13}{16} + \frac{11}{12} = \frac{13 \cdot 3}{16 \cdot 3} + \frac{11 \cdot 4}{12 \cdot 4} = \frac{39}{48} + \frac{44}{48} = \frac{83}{48} = 1\frac{35}{48}\] 8) \[\frac{12}{27} - \frac{5}{18} = \frac{12 \cdot 2}{27 \cdot 2} - \frac{5 \cdot 3}{18 \cdot 3} = \frac{24}{54} - \frac{15}{54} = \frac{9}{54} = \frac{1}{6}\]