ANSWER: They are 500 years between 300BCE and 200CE
EXPLANATION:
BCE = Before Common Era.
CE = Common Era.
The date of BCE stopped at the birth of Christ. This date is also known as before Christ. While the date of CE is the date that started at the birth of Christ, which some call AD ( Anno Domini).
To calculate how many years that are between two BCE you subtract the years.
To calculate how many years that's are between two CE, you subtract the years.
To calculate how many years are between BCE and CE, you add the years.
Therefore; The number of year that are between 300BCE and 200CE is:
300 + 200 = 500years.