This system has more unknowns than equations, so it is labeled an
"under-determined system", so it has infinitely many solutions.
The coefficient matrix is not a square matrix, thus it has no
inverse.  If you've studied left-inverse and right-inverses,
you may be able to get the general solution for the infinite
set of solutions that way, but you can get that easier just by 
ordinary methods:




Multiply 2nd equation by 2



Add them





Substitute in










There are infinitely many solutions.  Just substitute arbitrary 
values for z in the expressions above.  Here, I'll set up a 
computer program to generate some of them:

If you choose z=-21, then substituting, 
Also, 

If you choose z=-16, then substituting, 
Also, 

If you choose z=-11, then substituting, 
Also, 

If you choose z=-6, then substituting, 
Also, 

If you choose z=-1, then substituting, 
Also, 

If you choose z=4, then substituting, 
Also, 

If you choose z=9, then substituting, 
Also, 

If you choose z=14, then substituting, 
Also, 

If you choose z=19, then substituting, 
Also, 
 
I chose those value because they give integer solutions, however,
you can get fractional solutions by choosing other values for z.

Edwin