Since this is basically a ratio problem and we are given three values we can use the rule of three to solve for the missing variable which would be the total amount of trouts in the lake. To do so we multiply the total amount trouts tagged by the number of trouts caught later. Then we multiply that product by the amount that were found to be tagged later.
22 total trouts caught later <=========> 11 trouts were tagged
x total trouts <=========> 174 trouts tagged
(174 * 22) / 11 = 348 total trouts in the lake
Finally, we can see that the conservationist would expect there to be around 348 trouts in the lake.
