Question

Find the determinant of m by row reduction to echelon form

Answer 1

I will assume that you can reduce a matrix to row echelon form to get the matrix. This is also known as an upper triangular matrix.

Calculating the determinant is simple from here and it doesn't matter what the size of the matrix is. The determinant is simply the product of the diagonal, in this case
a11:a22:a33:a44

Remember that you can only calculate the determinant for square matrices.