б) (7 2/5 - 5 4/5) : 2 1/5

б) \((7 \frac{2}{5} - 5 \frac{4}{5}) : 2 \frac{1}{5} = (\frac{37}{5} - \frac{29}{5}) : \frac{11}{5} = \frac{8}{5} : \frac{11}{5} = \frac{8}{5} \cdot \frac{5}{11} = \frac{8}{11}\)