Solving Simultaneous Equations with Excel

[soleimani1967]

We can solve simultaneous equations with excel by using of SOLVER or MINVERSE matrix, if there is a constant value into our equations. My problem is: How we can solve simultaneous equations without the constant value such as below example?

2x + 3y + 8z = 0
5x – 2y + 4z = 0
7x + 5y – 3z = 0

[shg]

Same way, but it's trivial: x=y=z=0

[soleimani1967]

What about below example:
x – y = 0
y – x = 0
The answer is: x = y = c and “c” is a constant value.
How can we get this constant value by excel? In fact, I am willing to know how we can calculate eigenvector of matrix by using excel, if we have eigenvalue of matrix?