a) $$6 + 8\frac{7}{13} = (6+8) + \frac{7}{13} = 14\frac{7}{13}$$.
б) $$12 + 19\frac{5}{24} = (12+19) + \frac{5}{24} = 31\frac{5}{24}$$.
в) $$5\frac{7}{15} + 8\frac{4}{15} = (5+8) + (\frac{7}{15} + \frac{4}{15}) = 13 + \frac{7+4}{15} = 13 + \frac{11}{15} = 13\frac{11}{15}$$.
г) $$13\frac{5}{101} + 7\frac{25}{101} = (13+7) + (\frac{5}{101} + \frac{25}{101}) = 20 + \frac{5+25}{101} = 20 + \frac{30}{101} = 20\frac{30}{101}$$.
д) $$4\frac{3}{7} + 15\frac{4}{7} = (4+15) + (\frac{3}{7} + \frac{4}{7}) = 19 + \frac{3+4}{7} = 19 + \frac{7}{7} = 19 + 1 = 20$$.
e) $$3\frac{9}{13} + 4\frac{8}{13} = (3+4) + (\frac{9}{13} + \frac{8}{13}) = 7 + \frac{9+8}{13} = 7 + \frac{17}{13} = 7 + 1\frac{4}{13} = 8\frac{4}{13}$$.
Ответ: a) 14$$\frac{7}{13}$$; б) 31$$\frac{5}{24}$$; в) 13$$\frac{11}{15}$$; г) 20$$\frac{30}{101}$$; д) 20; e) 8$$\frac{4}{13}$$