1. Выполните действия: a) $$23\frac{11}{15} + 15\frac{6}{20}$$; б) $$60 - 31\frac{16}{35}$$; в) $$27\frac{17}{28} - 19,6 + 16\frac{18}{22}$$.

a) $$23\frac{11}{15} + 15\frac{6}{20} = 23\frac{22}{30} + 15\frac{9}{30} = 38\frac{31}{30} = 39\frac{1}{30}$$

б) $$60 - 31\frac{16}{35} = 59\frac{35}{35} - 31\frac{16}{35} = 28\frac{19}{35}$$

в) $$27\frac{17}{28} - 19,6 + 16\frac{18}{22} = 27\frac{17}{28} - 19\frac{6}{10} + 16\frac{9}{11} = 27\frac{17}{28} - 19\frac{3}{5} + 16\frac{9}{11} = 27\frac{17 \cdot 55}{28 \cdot 55} - 19\frac{3 \cdot 308}{5 \cdot 308} + 16\frac{9 \cdot 140}{11 \cdot 140} = 27\frac{935}{1540} - 19\frac{924}{1540} + 16\frac{1260}{1540} = (27 - 19 + 16) + \frac{935 - 924 + 1260}{1540} = 24 + \frac{1271}{1540} = 24\frac{1271}{1540}$$