Check out this beginner tutorial on how to solve a sudoku intermediate number puzzle.
Each sudoku has a unique solution that can be reached logically without guessing. Enter digits from 1 to 9 into the blank spaces. Every row must contain one of each digit. So must every column, as must every 3x3 square.
Sudoku is very simple to learn, it needs no calculations, and provides an amazing variety of logic situations. All that's required is brain power and concentration. Get the rules straight and try one out for yourself.