л) 5$$\frac{7}{8}$$ - $$\frac{9}{10}$$ = 5$$\frac{35}{40}$$ - $$\frac{36}{40}$$ = 4$$\frac{75}{40}$$ - $$\frac{36}{40}$$ = 4$$\frac{39}{40}$$
Ответ: 4$$\frac{39}{40}$$