The procedure is to make the difference of the terms that occupy the same position (column and row):
| - 6 - 4 | | - 5 5 | | - 6 + 5 - 4 - 5 | | -1 - 9 |
| 6 0 | - | - 4 -1 | = | 6 + 4 0 + 1 | = | 10 1 |
| 6 4 | | 6 - 4 | | 6 - 6 4 + 4 | | 0 8 |
Answer: option B.