Write down linear system describing the flow in the network

Question

Network question

I currently have the following answer:

X1 - X2 - X3 - X4 = 0
X2 = 1
X3 = -1
X4 = 5

But the answer sheet says this is correct:

X1 = 1
X1 - X2 - X3 - X4 = 0
X2 = 1
X3 = 1
X4 = 3

Is the answer sheet wrong? Or am I doing wrong? Thanks in advance.

Answer 1

Looking the picture I see:

$$ 1+x_2=2\rightarrow x_2=1\\ x_1=x_2+x_3+x_4\\ 2+x_3+1=2 \rightarrow x_3=-1\\ x_4=4+1=5 $$