$$\frac{a^{5,58} \cdot a^{2,9}}{a^{6,48}} = \frac{a^{5,58 + 2,9}}{a^{6,48}} = \frac{a^{8,48}}{a^{6,48}} = a^{8,48 - 6,48} = a^2 = 7^2 = 49$$.
Ответ: 49