А) 19/37:
$$
\frac{19}{37} = 0.\overline{513} = 0 + \frac{1}{\frac{1}{513}}
= 0 + \frac{1}{\frac{1}{\frac{1}{19}}}
= [0; 19, 513]
$$

б) -49/30:
$$
-\frac{49}{30} = -1\frac{19}{30} = -1 - \frac{1}{\frac{30}{49}}
= -1 - \frac{1}{\frac{1}{1}\frac{19}{30}}
= [-1; 1, 19, 2]
$$

в) 81/71:
$$
\frac{81}{71} = 1\frac{10}{71} = 1 + \frac{1}{\frac{71}{10}}
= 1 + \frac{1}{7\frac{1}{10}}
= [1; 7, 10]
$$