\( \frac{21x^8y^{13}}{14x^4y^{24}} = \frac{3 \cdot 7 \cdot x^8 \cdot y^{13}}{2 \cdot 7 \cdot x^4 \cdot y^{24}} \)
\( \frac{x^8}{x^4} = x^{8-4} = x^4 \)
\( \frac{y^{13}}{y^{24}} = y^{13-24} = y^{-11} = \frac{1}{y^{11}} \)
\( \frac{3}{2} \cdot x^4 \cdot \frac{1}{y^{11}} = \frac{3x^4}{2y^{11}} \)
Ответ: \( \frac{3x^4}{2y^{11}} \).