д) 4+15; 7 e) 3+48 13 г) 100 - 20.

д) $$4\frac{3}{7} + 15\frac{4}{7} = (4+15) + (\frac{3}{7} + \frac{4}{7}) = 19 + \frac{3+4}{7} = 19 + \frac{7}{7} = 19 + 1 = 20$$

е) $$3\frac{9}{13} + 4\frac{8}{13} = (3 + 4) + (\frac{9}{13} + \frac{8}{13}) = 7 + \frac{9+8}{13} = 7 + \frac{17}{13} = 7 + 1\frac{4}{13} = 8\frac{4}{13}$$

г) $$100 - 20\frac{3}{14} = 99\frac{14}{14} - 20\frac{3}{14} = (99 - 20) + (\frac{14}{14} - \frac{3}{14}) = 79 + \frac{14-3}{14} = 79 + \frac{11}{14} = 79\frac{11}{14}$$

Ответ: д) 20; е) $$8\frac{4}{13}$$; г) $$79\frac{11}{14}$$