Question

To estimate the size of the grizzly bear population in a national park, rangers tagged and released 12 grizzly bears into the park. A few months later, 2 out of 21 grizzly bears sighted were tagged. Assuming the population of tagged bears in the population, estimate the number of grizzly bears in the population of this national park.

Answer 1

same ratio, but not sure how good the estimate is

Answer 2

1/6 of the bears tagged were sighted (21).
To see all 12 tagged bears, you need to see 6 times the number of the sample.
21x6=126