Consider the following set of linear algebraic equations

$x{_1} + 2x{_2} + 3x{_3} = 2$

$x{_2} + x{_3} = -1$

$2x{_2} + 2x{_3} = 0$

The system has

1. a unique solution
2. no solution
3. an infinite number of solutions
4. only the trivial solution