Final answer:
After 3 half-lives of carbon-14, approximately 26.25 grams will remain out of the initial 210 grams.
Step-by-step explanation:
The half-life of carbon-14 is 5,730 years.
After each half-life, the amount of carbon-14 remaining is halved.
So, after 3 half-lives, the amount of carbon-14 remaining would be one-eighth of the original amount.
Starting with 210 grams of carbon-14, after one half-life (5730 years), you would have 105 grams remaining.
After the second half-life (11,460 years), you would have 52.5 grams remaining.
And after the third half-life (17,190 years), you would have 26.25 grams remaining.
Therefore, after 3 half-lives, you would have approximately 26.25 grams of carbon-14 remaining.