Row - reduction method :

The system of equations are

Write the equations in to matrix form.

Ax = B

Start with A next to I.

From the augmented matrix : [ A | I ].

So, inverse matrix .

b).

Note : \ \

The matrix  multiplied by its inverse yields the identity matrix.

.

So, the matrix which we have found  is the desired inverse.

c).

If A is a invertible matrix, the inverse matrix could be used to transform B into X.

.

Where A  is coefficient matrix , X  is variable matrix and B  is constant matrix.

The solution of the system is x = - 1330, y = - 70, and z = 40.