2) Вычислите: a) $$\frac{7}{9} + \frac{1}{9}$$ б) $$\frac{6}{15} - ?$$ в) $$\frac{17}{23} - \frac{6}{23} + 1$$ г) $$\frac{1}{2} - \frac{1}{8}$$ д) $$\frac{9}{12} ?$$ ж) $$\frac{4}{7} \cdot \frac{14}{8}$$ з) ? и) $$\frac{4}{17} : \frac{3}{17}$$ й) $$\frac{3}{4} : \frac{3}{4}$$

а) $$\frac{7}{9} + \frac{1}{9} = \frac{7+1}{9} = \frac{8}{9}$$ в) $$\frac{17}{23} - \frac{6}{23} + 1 = \frac{17-6}{23} + 1 = \frac{11}{23} + 1 = 1\frac{11}{23}$$ г) $$\frac{1}{2} - \frac{1}{8} = \frac{4}{8} - \frac{1}{8} = \frac{3}{8}$$ ж) $$\frac{4}{7} \cdot \frac{14}{8} = \frac{4 \cdot 14}{7 \cdot 8} = \frac{4 \cdot 2 \cdot 7}{7 \cdot 4 \cdot 2} = 1$$ и) $$\frac{4}{17} : \frac{3}{17} = \frac{4}{17} \cdot \frac{17}{3} = \frac{4 \cdot 17}{17 \cdot 3} = \frac{4}{3} = 1\frac{1}{3}$$ й) $$\frac{3}{4} : \frac{3}{4} = 1$$