Please help xxxxxxxx

Answer:
Step-by-step explanation:
a. [tex]\left(5\times \:10^3\right)\left(9\times \:10^7\right)[/tex]
[tex]5\times 10^3 = 5000\\\\5000\times \:9\times \:10^7[/tex]
[tex]\mathrm{Multiply\:the\:numbers:}\:5000\times \:9=45000[/tex]
[tex]=45000\times \:10^7[/tex]
b. [tex]\left(7\times 10^5\right)\div \left(2\times 10^2\right)[/tex]
[tex]\left(7\times 10^5\right)\div \left(2\times 10^2\right)=\frac{7\times \:10^5}{2\times \:10^2}[/tex]
[tex]\frac{10^5}{10^2} = 10^3[/tex]
[tex]\frac{7\times \:10^3}{2}[/tex]
[tex]\mathrm{Factor}\:\: 10^3 : 2^3\times5^3[/tex]
[tex]\frac{7\times \:2^3\times \:5^3}{2}[/tex]
[tex]\frac{2^3}{2}=2^2[/tex]
[tex]7\times \:2^2\times \:5^3=3500[/tex]