2.1*10^8 is how many times the value of 4.2*10^2

Which choice represents the sample space ,s for this event

What is the number 321,000,000 in scientific notation? also what is the number? ?

Hector and alex traded video games. alex gave hector one fourth of his video games in exchange for 6 video games. then he sold 3 video games and gave 2 video games to his brother. alex ended up with 16 video games. how many video games did alex have when he started?