55-64-

$$5\frac{1}{3} - 6\frac{1}{4} = \frac{16}{3} - \frac{25}{4} = \frac{16 \cdot 4}{3 \cdot 4} - \frac{25 \cdot 3}{4 \cdot 3} = \frac{64}{12} - \frac{75}{12} = \frac{64 - 75}{12} = \frac{-11}{12} = -\frac{11}{12}$$

Ответ: $$\frac{-11}{12}$$