$x+2y+z=4$

$2x+y+2z=5$

$x-y+z=1$

The system of algebraic equations given above has

1. a unique solution of $x=1$, $y=1$ and $z=1$
2. only the two solutions of $(x=1, y=1, z=1)$ and $(x=2, y=1, z=0)$
3. infinite number of solutions
4. no feasible solution