The three Ms for today are mental_floss, Monday, and Math Square. Enjoy!
The nine white squares inside the main red grid should be filled with the digits 1 through 9. Each digit should appear only once in this main grid (the red square). Place the digits 1 through 9 in their correct spots so that the mathematical equations work both across and down.
Here is the SOLUTION.
NOTE: These puzzles rarely (but occasionally) have alternate solutions that fit the rules. If you find one of these, first... READ ON