How to find $a, b$ and $c$ from this system of linear equations? Find $a$, $b$ and $c$ from:
$$
\begin{align}
a+c &= 3 \\
b+a &= 2  \\
c+b &= -1 \\
\end{align}
$$
I tried the following way, the answer comes wrong:
$$(a+c) + (b+a) = 3+2$$

$$(a+c)+(c+b)+(b+a)=3+2-1$$
$$2(a+b+c)=4$$
$$a+b+c=2$$
Then if $a+b+c=2$ and $a+c=3$ then $b=-1$
Then if $a+b+c=2$ and $a+b=2$ then $c=0$
Then if $a+b+c=2$ and $b+c=-1$ then $a=3$
