А) 19/37:

$$\frac{19}{37} = 0.\overline{513} = 0 + \cfrac{1}{1 + \cfrac{1}{3 + \cfrac{1}{7}}}$$

б) -49/30:

$$-\frac{49}{30} = -1\frac{19}{30} = -1 - \frac{1}{\frac{30}{19}} = -1 - \cfrac{1}{1 + \cfrac{11}{19}}$$

в) 81/71:

$$\frac{81}{71} = 1\frac{10}{71} = 1 + \frac{1}{\frac{71}{10}} = 1 + \cfrac{1}{7 + \cfrac{1}{10}}$$