Вычислите:
а) $\frac{3}{8} + \frac{3}{20}$;
б) $\frac{5}{6} - \frac{3}{8}$;
в) $\frac{8}{15} + \frac{4}{9}$;
г) $\frac{5}{12} - \frac{2}{9}$;
д) $\frac{5}{6} + \frac{3}{10}$;
е) $\frac{7}{20} - \frac{7}{30}$.
$\frac{3}{8} + \frac{3}{20} = \frac{3 * 5 + 3 * 2}{40} = \frac{15 + 6}{40} = \frac{21}{40}$
$\frac{5}{6} - \frac{3}{8} = \frac{5 * 4 - 3 * 3}{24} = \frac{20 - 9}{24} = \frac{11}{24}$
$\frac{8}{15} + \frac{4}{9} = \frac{8 * 3 + 4 * 5}{45} = \frac{24 + 20}{45} = \frac{44}{45}$
$\frac{5}{12} - \frac{2}{9} = \frac{5 * 3 - 2 * 4}{36} = \frac{15 - 8}{36} = \frac{7}{36}$
$\frac{5}{6} + \frac{3}{10} = \frac{5 * 5 + 3 * 3}{30} = \frac{25 + 9}{30} = \frac{34}{30} = \frac{17}{15} = 1\frac{2}{15}$
$\frac{7}{20} - \frac{7}{30} = \frac{7 * 3 - 7 * 2}{60} = \frac{21 - 14}{60} = \frac{7}{60}$
Пожауйста, оцените решение