\( \frac{2}{7} - \frac{4}{14} = \frac{2 \cdot 2 - 4}{14} = \frac{4 - 4}{14} = 0 \)
\( \frac{4}{15} \cdot 0 = 0 \)
\( 4 + \frac{20}{23} + 0 = 4 + \frac{20}{23} = \frac{4 \cdot 23 + 20}{23} = \frac{92 + 20}{23} = \frac{112}{23} \)
Ответ: 112/23