I’ve been out of school a long time (I mean a long time), yet I think I’m still pretty good at basic math. I’m always able to figure out whether a “bargain buy” at the supermarket is actually a ...

She’s right—using simultaneous equations does get really complicated, and if you’d like to send me your work for the solution, I’d love to see it. But the system is also kind of a trick. Like a sudoku ...