\[ \frac{a^{15} \cdot a^9}{a^{22}} = \frac{a^{15+9}}{a^{22}} = \frac{a^{24}}{a^{22}} = a^{24-22} = a^2 \]
\[ a^2 = 4^2 = 16 \]
Ответ: 16