Ответ:

1) \(\frac56\cdot\frac3{20}=\frac18\).

2) \(\frac37\cdot\frac6{11}=\frac{18}{77}\).

3) \(\frac{10}{11}\cdot\frac{11}{26}=\frac5{13}\).

4) \(\frac{24}{65}\cdot\frac{39}{40}=\frac9{25}\).

Ответ: 1) \(\frac18\); 2) \(\frac{18}{77}\); 3) \(\frac5{13}\); 4) \(\frac9{25}\).