Chapter 7 - Exponents and Exponential Functions - 7-3 Multipying Powers with the Same Base - Practice and Problem-Solving Exercises - Page 430: 52

$8 \times 10^{5}$

$a^m \cdot a^n = a^{m+n}$ Multiply the corresponding parts and use the rule above when necessary to obtain: $=(8\cdot 0.1) \times (10^{-3} \cdot 10^{9}) \\=0.8 \times 10^{-3+9} \\=0.8 \times 10^{6} \\=(8)(10^{-1}) \times 10^{6} \\=8 \times 10^{-1+6} \\=8 \times 10^{5}$