Some puzzles I've found to be interesting

I have found these puzzles quite interesting. If you enjoy puzzles (at least some of the time), perhaps you will enjoy them. They are listed in what strikes me as increasing order of difficulty. Hints and/or solutions may be available, depending on the puzzle.

1. 4 integers between 100 and 999, inclusive, which equal the sum of the cubes of their digits
2. 4 integers that can be combined with + or - to make the numbers 1 through 40
3. 12 apparently identical coins and a scale that can be used 3 times only

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