You need to make it so that all the numbers from 1 to 8 appear once in every row and column. You can only do that by "pushing" the columns down and the rows left. Each time you "push" a row or a column all the numbers in it move one block in the direction you have pushed it.
6 | 4 | 8 | 6 | 8 | 7 | ||||||||||||||
1 | 3 | 1 | 2 | 5 | 6 | ||||||||||||||
7 | 4 | 2 | 8 | 5 | 4 | 2 | 2 | ||||||||||||
7 | 5 | 3 | 7 | 5 | 3 | 1 | 3 | ||||||||||||
3 | 8 | 4 | 7 | 5 | 6 | 2 | 1 | ||||||||||||
6 | 3 | 1 | 6 | 1 | 4 | 7 | 8 | ||||||||||||
2 | 5 | 4 | 3 | 4 | 5 | 2 | 1 | ||||||||||||
7 | 2 | 1 | 3 | 6 | 4 | 8 | 7 | ||||||||||||
8 | 6 | ||||||||||||||||||
5 | 8 | ||||||||||||||||||
