it is given but i suppose it is
So now to solve the linear equations let us first have our augmented matrix
Now that we have got here we see that in question it is given that this linear equations have infinitely many solutions so the value of must be zero otherwise we would get 3 independent rows that would imply that the matrix is invertible and we will be left with only one solution for any right hand side.
as we make as zero also we see that also be zero as it will make the equations consistent
from above we conclude that the value of = -1.
So by putting the value in rthe equation we get the answer as 1.