Explanation:
out of the first equation we get
x = 2y - 3z - 1
this we use in the second equation
-3(2y - 3z - 1) + 6y - 9z = 3
-6y + 9z + 3 + 6y - 9z = 3
0 = 0
this is the same equation as the first one, just multiplied by -3.
and we see the third equation is again the same one as the first just multiplied by 2.
so, there are infinite solutions.
this has not a single solution, as in the end this is just one equation with 3 variables.