Is it possible tofind three unknowns with two equations?

Answerno.

A system with two equations and three variable is known as a parametric equation and can be simplified, generally, to one equation with two variables.

You always need a number of equations equal to or greater than the number of variables you have to find any of the variables.

If you have more varibles than equations you can eliminate a number of variables equal to the number of equations minus one.

Edit: While this is correct, you can fudge an answer using a pseudoinverse. This minimizes one of the values, and then you can approximate the other two. Suppose you have:

3x + 2y + 4z = 0

x + 8y + 7z = 3

You can call this A*b = y, where

A = [3,2,4;1,8,7]

b = [x;y;z]

y= [0;3]

Then you can say

b=ay, where

a=A'(A*A')^(-1)

' indicated the transpose, and ^-1 indicates the inverse.

More explanation can be found at http://neurotheory.columbia.edu/~ken/math-notes/sabes.pdf