5.281 Вычислите: a) 4 4/7 + 12 5/7; б) 9 8/15 + 6 13/15;

a) $$4\frac{4}{7} + 12\frac{5}{7} = (4+12) + (\frac{4}{7} + \frac{5}{7}) = 16 + \frac{9}{7} = 16 + 1\frac{2}{7} = 17\frac{2}{7}$$ б) $$9\frac{8}{15} + 6\frac{13}{15} = (9+6) + (\frac{8}{15} + \frac{13}{15}) = 15 + \frac{21}{15} = 15 + 1\frac{6}{15} = 16\frac{6}{15} = 16\frac{2}{5}$$