5. 15 -6

5. $$15 \frac{1}{10} - 6 \frac{4}{10} = (15-6) + (\frac{1}{10} - \frac{4}{10}) = 9 + (\frac{1}{10} - \frac{4}{10}) = 9 - \frac{3}{10} = 8 \frac{7}{10}$$

Ответ: $$8 \frac{7}{10}$$