2/5 * 3/4 = ?

$$\frac{2}{5} \cdot \frac{3}{4} = \frac{2 \cdot 3}{5 \cdot 4} = \frac{6}{20}$$
Сократим дробь на 2:
$$\frac{6}{20} = \frac{6:2}{20:2} = \frac{3}{10}$$

Ответ: 3/10