please im doing a test i need HELP URGENTLY!!!!!! I BEG YOU GUYS!!**you must be sure about the answer ok?! PLEASE..AND thank you....

Simplify each expression using the laws of exponents to see if they are equal to the given number.
Remember the following:
[tex]\begin{gathered} a^n\times a^m=a^{n+m} \\ \frac{a^n}{a^m}=a^{n-m} \end{gathered}[/tex]First expression:
[tex]\begin{gathered} (2\times10^8)(2\times10^{-2})=2\times2\times10^8\times10^{-2} \\ =4\times10^{8-2} \\ =4\times10^6 \end{gathered}[/tex]Second expression:
[tex]\begin{gathered} 40\times10^5=4\times10\times10^5 \\ =4\times10^{5+1} \\ =4\times10^6 \end{gathered}[/tex]Third expresion:
[tex]\begin{gathered} 40^6=(4\times10)^6 \\ =4^6\times10^6 \\ =4096\times10^6 \end{gathered}[/tex]Fourth expression:
[tex]\begin{gathered} 400,000=4\times100,000 \\ =4\times10^5 \end{gathered}[/tex]Fifth expression:
[tex]\begin{gathered} \frac{1.2\times10^9}{3\times10^2}=\frac{1.2\times10\times10^8}{3\times10^2} \\ =\frac{12\times10^8}{3\times10^2} \\ =\frac{12}{3}\times\frac{10^8}{10^2} \\ =4\times10^{8-2} \\ =4\times10^6 \end{gathered}[/tex]