|Spoiler Inside: Solution to Puzzle||SelectShow>|
A common way to solve logic problems is to make a grid showing how each of the categories intersects with each of the others.
Per clue 1, John has the dog and does not live in the apartment, and the apartment dweller has a cat.
Per clue 3, John can not live in the dorm room. Therefore, he lives in the house.
Per clue 2, Gordon lives in the dorm room. Therefore, Sue lives in the apartment (and has the cat). Therefore, Gordon has the goldfish.
The solution is: