The first step to finding your answer is to remove the first set of parenthesis.
3 x [tex]10^{9} [/tex] x ( 2 x [tex] 10^{17} [/tex] )
Then remove the second set of parenthesis.
3 x [tex]10^{9} [/tex] x 2 x [tex] 10^{17} [/tex]
Now multiply 3 and 2 together
6 x [tex]10^{9} [/tex] x [tex] 10^{17} [/tex]
In order to multiply terms with the same base,, you must instead just add their exponents together. This will look like the following:
6 x [tex] 10^{9 + 17} [/tex]
This means that the answer to your question will be 6 x [tex] 10^{26} [/tex] when put in scientific notation.
Let me know if you have any further questions
:)