Решение:

1. $$8\frac{4}{15}+2\frac{11}{15} = (8 + 2) + (\frac{4}{15} + \frac{11}{15}) = 10 + \frac{15}{15} = 10 + 1 = 11$$
2. $$4\frac{5}{9}+3\frac{7}{9} = (4 + 3) + (\frac{5}{9} + \frac{7}{9}) = 7 + \frac{12}{9} = 7 + 1\frac{3}{9} = 8\frac{3}{9} = 8\frac{1}{3}$$
3. $$5\frac{7}{24}+7\frac{5}{24} = (5 + 7) + (\frac{7}{24} + \frac{5}{24}) = 12 + \frac{12}{24} = 12 + \frac{1}{2} = 12\frac{1}{2}$$

Ответ:

1. $$\mathbf{11}$$
2. $$\mathbf{8\frac{1}{3}}$$
3. $$\mathbf{12\frac{1}{2}}$$