Final answer:
When 50% of the original Element X is still remaining, the number of years that have gone by is equal to the half-life of 5,700 years.
Step-by-step explanation:
The question asks about the amount of time that has passed when 50% of the original Element X is still remaining, given a half-life of 5,700 years. To find the answer, we need to determine how many half-lives have occurred when 50% is remaining. Since each half-life reduces the amount by half, if 50% is remaining, it means that one half-life has occurred. Therefore, the time that has passed is equal to the half-life, which is 5,700 years.