The sudoku rules explained: the start

At the start of a game some fields are already populated with numbers. This is done in such a way that the puzzle can be solved with logic and that there is only one solution. There are different tactics to be able to determin the correct numbers in the empty fields

3 2 4
3 4 6 2 9 5
5 7 6
8 4
7 5 9
9 6 3 8 7
9 2
7 4