Solve the following multiplications of fractions:

Решение:

1. \( -\frac{3}{4} \cdot \frac{4}{9} = -\frac{3 \cdot 4}{4 \cdot 9} = -\frac{12}{36} = -\frac{1}{3} \)
2. \( \frac{7}{9} \cdot \frac{18}{35} = \frac{7 \cdot 18}{9 \cdot 35} = \frac{7 \cdot (2 \cdot 9)}{(9) \cdot (5 \cdot 7)} = \frac{2}{5} \)
3. \( -\frac{4}{19} \cdot \left( -\frac{57}{64} \right) = \frac{4}{19} \cdot \frac{57}{64} = \frac{4 \cdot 57}{19 \cdot 64} = \frac{4 \cdot (3 \cdot 19)}{(19) \cdot (16 \cdot 4)} = \frac{3}{16} \)

Ответ: \( -\frac{1}{3}; \frac{2}{5}; \frac{3}{16} \)