# How do you find the determinant of ((10, 10, 5), (10, 10, 8), (10, 10, 9))?

The determinant is $0$ since the first two columns are linearly dependent.
Since the first two columns are identical, the effect of multiplying by this matrix is a linear transform which squashes at least one dimension, reducing the unit cube to zero volume. So the determinant is $0$.