Place each number once so every row and column hits its target — by adding, subtracting, multiplying or dividing.
The full guide, with a worked example and common mistakes: How to play Magic grid puzzles.
In Magic Difference and Magic Division, the first cell of a row or column. You start from it and subtract or divide the others in turn.
Yes, for Magic Sum: the Magic Sum Solver explains every step.
Magic Sum is the gentlest. Product builds times-table fluency; Mixed is the hardest.