Any number between 250 and 350 - including 250, but not including 350 (depending on the exact rules used, actually).
300
300
300
300
300
300
300
It is 300 when rounded to the nearest hundred
300
300
When rounding 320 to the nearest hundred, you look at the digit in the tens place, which is 2. Since 2 is less than 5, you round down. Therefore, 320 rounded to the nearest hundred is 300.
207 rounded to the nearest hundred is 200