Задание от Пухли

Решим примеры: а) $$\frac{7}{9} + \frac{1}{9} = \frac{7+1}{9} = \frac{8}{9}$$ б) $$\frac{6}{15} - \frac{4}{15} = \frac{6-4}{15} = \frac{2}{15}$$ в) $$\frac{17}{23} - \frac{6}{23} + 1 = \frac{17-6}{23} + 1 = \frac{11}{23} + 1 = \frac{11}{23} + \frac{23}{23} = \frac{34}{23} = 1 \frac{11}{23}$$ г) $$\frac{4}{9} + \frac{1}{3} = \frac{4}{9} + \frac{3}{9} = \frac{4+3}{9} = \frac{7}{9}$$ д) $$\frac{1}{2} - \frac{1}{8} = \frac{4}{8} - \frac{1}{8} = \frac{4-1}{8} = \frac{3}{8}$$ е) $$\frac{9}{12} + \frac{3}{4} - \frac{1}{6} = \frac{9}{12} + \frac{9}{12} - \frac{2}{12} = \frac{9+9-2}{12} = \frac{16}{12} = \frac{4}{3} = 1 \frac{1}{3}$$ ж) $$\frac{4}{7} \cdot \frac{14}{8} = \frac{4 \cdot 14}{7 \cdot 8} = \frac{1 \cdot 2}{1 \cdot 2} = 1$$ з) $$\frac{9}{13} : \frac{5}{26} = \frac{9}{13} \cdot \frac{26}{5} = \frac{9 \cdot 26}{13 \cdot 5} = \frac{9 \cdot 2}{1 \cdot 5} = \frac{18}{5} = 3 \frac{3}{5}$$ и) $$\frac{4}{17} : \frac{3}{17} \cdot \frac{3}{4} = \frac{4}{17} \cdot \frac{17}{3} \cdot \frac{3}{4} = \frac{4 \cdot 17 \cdot 3}{17 \cdot 3 \cdot 4} = 1$$