this is how
1. Write your 3 x 3 matrix. More ↓
2. Choose a single row or column. ↓
3. Cross out the row and column of your first element. ↓
4. Find the determinant of the 2 x 2 matrix. ↓
5. Multiply the answer by your chosen element. ↓
6. Determine the sign of your answer. ↓
7. Repeat this process for the second element in your reference row or column. ↓
8. Repeat with the third element. ↓
9. Add your three results together. ↓
Hope this helps!
