Answer :
[tex](3.45x10^4)(5x10^5)[/tex]
To multiply numbers in scientific notation you multiply the numbers in the coefficient as norma, and then you add the powers of 10, as follow:
[tex]\begin{gathered} =(3.45)(5)x10^{4+5} \\ =17.25x10^9 \end{gathered}[/tex]As you get a number that is not in scientific notation you move the decimal point to the left and add 1 to the power of ten:
[tex]17.25x10^9=1.725x10^{10}[/tex]Then, after evaluate the expression you get: 1.75x10^10