\( \Large 81^{2.5} \times 9^{4.5} \div 3^{4.8} = 9^{?} \) => \( \Large \frac{81^{2.5} \times 9^{4.5}}{3^{4.8}} = 9^{?} \) => \( \Large \frac{ \left(3^{4}\right)^{2.5} \times \left(3^{2}\right)^{4.5} }{3^{4.8}} = 9^{?} \) => \( \Large \frac{3^{10} \times 3^{9}}{3^{4.8}} = 9^{?} \) => \( \Large 3^{10+9-4.8} = 9^{?} \) => \( \Large 9^{?} = 3^{14.2} \) => \( \Large \left(3\right)^{2 \times ?} = 3^{14.2} \) => \( \Large 2 \times ? = 14.2 \) Therefore, \( \Large ? = \frac{14.2}{2} = 7.1 \)
