55.-(-)

55. $$\frac{3}{8} - (-\frac{1}{9}) = \frac{3}{8} + \frac{1}{9} = \frac{3 \cdot 9}{8 \cdot 9} + \frac{1 \cdot 8}{9 \cdot 8} = \frac{27}{72} + \frac{8}{72} = \frac{35}{72}$$

Ответ: $$\frac{35}{72}$$