Mean, Median and Mode
This is a category that is not that hard, but can be really tricky if you are not careful. So get your basics straight :)
Definition of Mean and Median
1990 AJHSME Problem 20 Problem 23
1993 AJHSME Problem 11 Problem 15
2019 AMC 8 Problem 7 Problem 10
Average of Arithmetic Sequence
Average of Two Sets
Mean, Median and Mode involving a set with unknown numbers (hard)