Stolen Rubies (Solution)

I kind of cheated and just brute forced the solution for this one. I enumerated every possible way the scoundrel could put the rubies in the box following the rules. These are the ways.

box1	box2	box3
2	8	20
3	9	18
4	10	16
5	11	14
6	12	12
7	13	10
8	14	8
9	15	6
10	16	4
11	17	2

And then, for each I used google sheets to compute the number of rubies I would get for every possible guess for each of those. It’s a lot to show so here’s a screenshot.

Notice that if you guess 8 for each box you will win 16 rubies no matter how the scoundrel puts the rubies in teh box.