Sure! Let's solve these calculations:

### Bài 8:

1) \(-\frac{20}{41} - \frac{4}{5} = -\frac{20}{41} - \frac{32}{41} = -\frac{52}{41}\)

2) \(-\frac{24}{5} - \frac{15}{-8} = -\frac{24}{5} + \frac{15}{8} = -\frac{192}{40} + \frac{75}{40} = -\frac{117}{40}\)

3) \(\frac{17}{34} - \frac{-24}{-12} = \frac{1}{2} - 2 = -\frac{3}{2}\)

4) \(-\frac{20}{7} - \frac{5}{21} = -\frac{60}{21} - \frac{5}{21} = -\frac{65}{21}\)

5) \(-\frac{8}{5} - \frac{-12}{7} = -\frac{8}{5} + \frac{12}{7} = -\frac{56}{35} + \frac{60}{35} = \frac{4}{35}\)

6) \(-\frac{12}{21} : \frac{1}{6} = -\frac{12}{21} \cdot 6 = -\frac{72}{21} = -\frac{24}{7}\)

### Bài 9:

1) \(-\frac{3}{5} : \frac{4}{21} = -\frac{3}{5} \cdot \frac{21}{4} = -\frac{63}{20}\)

2) \(-\frac{3}{4} : \frac{1}{2} = -\frac{3}{4} \cdot 2 = -\frac{6}{4} = -\frac{3}{2}\)

3) \(-\frac{8}{15} \cdot \frac{1}{4} = -\frac{8}{60} = -\frac{2}{15}\)

4) \(\left(\frac{11}{15}\right) : \frac{1}{10} = \frac{11}{15} \cdot 10 = \frac{110}{15} = \frac{22}{3}\)

5) \(\frac{1}{5} : \left(-\frac{1}{5}\right) = \frac{1}{5} \cdot -5 = -1\)

6) \(\left(-\frac{3}{7}\right) \cdot \left(-\frac{6}{49}\right) = \frac{18}{343}\)

### Bài 10:

1) \(4,5 \cdot \left(-\frac{4}{9}\right) = -\frac{20}{9}\)

2) \(2,4 \cdot \left(-\frac{4}{7}\right) = -\frac{48}{35}\)

3) \(0,2 - \frac{-15}{4} = 0,2 + \frac{15}{4} = \frac{43}{20}\)

4) \(\left(-3,5\right) : \left(-\frac{2}{4}\right) = 3,5 \cdot 2 = 7\)

5) \(-\frac{5}{23} : \left(-2\right) = \frac{5}{46}\)

6) \(1,25 : \left(-\frac{3}{8}\right) = 1,25 \cdot -\frac{8}{3} = -\frac{10}{3}\)

### Bài 11:

1) \(-\frac{1}{4} : \frac{-3}{4} = \frac{1}{3}\)

2) \(\frac{2}{3} - \frac{-1}{3} + \frac{7}{15} = \frac{2}{3} + \frac{1}{3} + \frac{7}{15} = \frac{25}{15} = \frac{5}{3}\)

3) \(\frac{4}{5} - \left(-\frac{2}{5}\right) \cdot \frac{7}{10} = \frac{4}{5} + \frac{14}{50} = \frac{24}{25}\)

4) \(\frac{3}{2} : \frac{4}{3} \cdot \frac{7}{7} = \frac{9}{8}\)

5) \(\frac{2}{3} + \frac{-1}{4} : \frac{1}{3} = \frac{2}{3} - \frac{1}{4} \cdot 3 = \frac{2}{3} - \frac{3}{4} = -\frac{1}{12}\)

6) \(\frac{3}{5} : \frac{5}{4} + \frac{2}{5} = \frac{12}{25} + \frac{2}{5} = \frac{22}{25}\)

These are the calculations based on the given problems. Let me know if you have any questions!