They're right. I was wrong. It's a dependent system, not an inconsistent
system. It has many solutions. I didn't actually solve it. I noticed the variables had the same coefficients, did it in my head and missed a sign! Sorry!
There is no possible solution because
is an inconsistent system.
Edwin
It's a dependent system, not an inconsistent problem. But teachers should
warn you if they're going to give such problems.