3.

• $$\frac{1}{6} + \frac{3}{8} = \frac{1 \cdot 4}{6 \cdot 4} + \frac{3 \cdot 3}{8 \cdot 3} = \frac{4}{24} + \frac{9}{24} = \frac{13}{24}$$

Ответ: $$\frac{13}{24}$$