56 1- 3-

$$1{\frac{6}{7}} \cdot 3{\frac{5}{10}} = {\frac{13}{7}} \cdot {\frac{35}{10}} = {\frac{13\cdot35}{7\cdot10}} = {\frac{13\cdot7\cdot5}{7\cdot5\cdot2}} = {\frac{13}{2}} = 6{\frac{1}{2}}$$

Ответ: 6 1/2