Bradford T. answered 03/05/24
Retired Engineer / Upper level math instructor
For a closed model, matrix notation,
AX=X or AX=IX
For this case,
| 2/5 1/3 1/2 |
A = | 1/5 1/3 1/5 |
| 1/5 1/3 0 |
| 3/5 -1/3 -1/2 |
I-A = | -1/5 2/3 -1/5 |
| -1/4 -1/3 1 |
Using Gauss-Jordan elimination
x=3z/2 = 108
y=6z/5 = 86.4
z=72 which was given