Запишите недостающие числа. a) $$\frac{2}{3} + \frac{3}{4} = \frac{\square}{12} + \frac{\square}{12} = \frac{\square}{12}$$ б) $$\frac{2}{15} + \frac{7}{10} = \frac{\square}{30} + \frac{\square}{30} = \frac{\square}{30}$$ в) $$\frac{3}{16} + \frac{9}{20} = \frac{\square}{36} + \frac{\square}{36} = \frac{\square}{36}$$ д) $$\frac{1}{2} - \frac{1}{3} = \frac{\square}{6} - \frac{\square}{6} = \frac{\square}{6}$$ е) $$\frac{11}{36} - \frac{5}{18} = \frac{\square}{36} - \frac{\square}{36} = \frac{\square}{36}$$ ж) $$\frac{9}{10} - \frac{7}{8} = \frac{\square}{35} - \frac{\square}{35} = \frac{\square}{35}$$