1) $$\frac{4}{25} + \frac{15}{4} = \frac{4 \cdot 4}{25 \cdot 4} + \frac{15 \cdot 25}{4 \cdot 25} = \frac{16}{100} + $$ 2) $$\frac{9}{4} - \frac{8}{5} = \frac{9 \cdot 5}{4 \cdot 5} - \frac{8 \cdot 4}{5 \cdot 4} = \frac{45}{20} - \frac{32}{20} = $$ 3) $$\frac{3}{2} \cdot \frac{9}{5} = \frac{3 \cdot 9}{2 \cdot 5} = \frac{27}{10} = 2,7$$ 4) $$\frac{3}{4} : \frac{9}{25} = \frac{3}{4} \cdot \frac{25}{9} = \frac{3 \cdot 25}{4 \cdot 9} = \frac{1 \cdot 25}{4 \cdot 3} =$$

Решим каждый пример пошагово: 1) $$\frac{4}{25} + \frac{15}{4} = \frac{4 \cdot 4}{25 \cdot 4} + \frac{15 \cdot 25}{4 \cdot 25} = \frac{16}{100} + \frac{375}{100} = \frac{16+375}{100} = \frac{391}{100} = 3,91$$ 2) $$\frac{9}{4} - \frac{8}{5} = \frac{9 \cdot 5}{4 \cdot 5} - \frac{8 \cdot 4}{5 \cdot 4} = \frac{45}{20} - \frac{32}{20} = \frac{45-32}{20} = \frac{13}{20} = 0,65$$ 3) $$\frac{3}{2} \cdot \frac{9}{5} = \frac{3 \cdot 9}{2 \cdot 5} = \frac{27}{10} = 2,7$$ 4) $$\frac{3}{4} : \frac{9}{25} = \frac{3}{4} \cdot \frac{25}{9} = \frac{3 \cdot 25}{4 \cdot 9} = \frac{1 \cdot 25}{4 \cdot 3} = \frac{25}{12} = 2 \frac{1}{12}$$ Ответы: 1) 3,91 2) 0,65 3) 2,7 4) $$2 \frac{1}{12}$$