2) 8 5/12 - 6 7/20 ;

2) $$8 \frac{5}{12} - 6 \frac{7}{20} = (8 - 6) + (\frac{5}{12} - \frac{7}{20}) = 2 + (\frac{5 \cdot 5}{12 \cdot 5} - \frac{7 \cdot 3}{20 \cdot 3}) = 2 + (\frac{25}{60} - \frac{21}{60}) = 2 + \frac{4}{60} = 2 + \frac{1}{15} = 2 \frac{1}{15}$$

Ответ: $$2 \frac{1}{15}$$