Casework
Honestly, casework is just a way of organizing our thoughts so that we can count more systematically. To find the optimal way to list the cases, however, often requires us to utilize knowledge from other topics such as factoring, number theory, geometry... I put all questions where we need to list cases here, which explains the large number of questions in this category. Whenever a question calls for other skills to help with the casework, I include that question under the other skill as well.
1991 AJHSME Problem 11 (not exactly casework, but this problem is so simple I have nowhere else to put it...)
1992 AJHSME Problem 7 (OK, so there are not that many cases here, still...)
1994 AJHSME Problem 8 Problem 24
AIME LEVEL PROBLEMS
2019 AIME I Problem 4 Problem 9
2020 AIME II Problem 9 Problem 12
2021 AIME I Problem 1 Problem 3
2022 AIME I Problem 6 Problem 12 Problem 13
2022 AIME II Problem 2 Problem 5 (using the property of prime) Problem 8
2023 AIME I Problem 6 Problem 7
2024 AIME II Problem 9 Problem 15