The sum of the weights of 8 children is 520 pounds. No two children have the same weight. What is the average(mean) weight of he fourth and fifth heaviest children if the mean and median

Answer 1

since you do not in fact specify anything about the mean and median, there are many possible answers.

Some possible set of weights are arithmetic sequences:
2, 20, 38, ..., 128
...
51, 53, 55, ..., 65