Question 371030
1.{{{a+b+c=-3}}}
2.{{{3b-c=4}}}
3.{{{2a-b-2c=-5}}}
Multiply eq. 1 by  (-2) and add to eq. 3,
{{{-2a-2b-2c+2a-b-2c=6-5}}}
4.{{{-3b-4c=1}}}
Add eq. 2 to eq. 4,
{{{3b-c-3b-4c=4+1}}}
{{{-5c=5}}}
{{{highlight(c=-1)}}}
Then from eq. 2,
{{{3b+1=4}}}
{{{3b=3}}}
{{{highlight(b=1)}}}
From eq. 1,
{{{a+1-1=-3}}}
{{{highlight(a=-3)}}}