13 5 14 42 -- --

$$\frac{13}{14} - \frac{5}{42} = \frac{13 \cdot 3}{14 \cdot 3} - \frac{5}{42} = \frac{39}{42} - \frac{5}{42} = \frac{34}{42} = \frac{17}{21}$$

Ответ: $$\frac{17}{21}$$