Problem
Her monthly income is $1500 weekly, which she uses for buying various quantities of goods X and Y,
Assume the following set of equations:
3x - y + 2z = 14
-x + 2y - 4z = 20
2x -3y + 4z = 5
1. Put the system of equations into matrix form;
2. Find its matrix of co-factors;
3. What is the determinant of this matrix?
4. Prove that the value of the determinant in (3) is correct.