Ответ:
$$\frac{4}{13} + \frac{3}{13} \cdot (\frac{5}{1} + \frac{1}{39}) = \frac{4}{13} + \frac{3}{13} \cdot (\frac{5 \cdot 39}{39} + \frac{1}{39}) = \frac{4}{13} + \frac{3}{13} \cdot (\frac{195}{39} + \frac{1}{39}) = \frac{4}{13} + \frac{3}{13} \cdot \frac{196}{39} = \frac{4}{13} + \frac{3 \cdot 196}{13 \cdot 39} = \frac{4}{13} + \frac{588}{507} = \frac{4}{13} + \frac{196}{169} = \frac{4 \cdot 13}{13 \cdot 13} + \frac{196}{169} = \frac{52}{169} + \frac{196}{169} = \frac{248}{169}$$
