linear algebra – what happens if i cant make a perfect triangle form gaussian elimination? and what does a determinant represent?

say I have a matrix of begin{bmatrix}7&2&2&8\0&6&8&13\0&0&0&9\0&0&0&10end{bmatrix}
would I just need to start over from the beginning until I have a proper triangle or is there a way to solve this from the matrix without using a different method?

I also have no idea what a determinant represents without abstraction