Answer:
522
Step-by-step explanation:
The assumption is that the proportion of tagged fish caught is the same as the proportion of all fish that were caught and tagged:
(all fish)/(number tagged) = (sample size)/(number in sample tagged)
all fish = (number tagged) · (sample size)/(number in sample tagged)
all fish = 174 · 39/13
all fish = 522
If all the assumptions are reasonable, the number of fish in the lake is estimated at 522.
