Hidden Numbers in Sudoku Puzzles.
This is a very simple method for finding the solution of a cell. You can find hidden numbers in almost every Sudoku puzzle. Just follow the guidelines hereafter: Start by looking for a possible solution in each row, column or box, which appears only once in the row, column of box. Since the possible solution appears only once, the possible solution has to be the solution for the concerned cell. All other numbers in the cell can be eliminated.
Cell A1 contains the number (1). This number doesn't appear anywhere else in the green box (or even in the first column). This means that the number (1) has to be the solution for cell A1. All the other numbers in cell A1 can be eliminated.