Line up the i's with like subscripts vertically:
Make the denominator determinant D, whose elements are all
the coefficients of the i's on the left of the equal signs:
Now we make the numerator determinants.
The numerator determinant for the 1st variable Di1 is formed by
replacing the 1st column of the denominator determinant D by the numbers on the
right of the equal signs:
The numerator determinant for the 2nd variable Di2 is formed by
replacing the 2nd column of the denominator determinant D by the numbers on the
right of the equal signs:
The numerator determinant for the 3rd variable Di3 is formed by
replacing the 3rdd column of the denominator determinant D by the numbers on the
right of the equal signs:
Finally, we put the numerators over the same denominator D:
Edwin