Can you solve this puzzle?
Place + and - signs between digits to make 100.
123456789

Check out this online version of the Kakooma Puzzle by Greg Tang. I recommend starting with the practice version (and of course read the directions). These supposedly take an average adult around 4 minutes to solve.

Can you solve this challenge that is based on the Proof card game?
https://www.proofmathgame.com/math-puzzles/76

Here is their archive of past challenges:
https://www.proofmathgame.com/math-puzzles/past