Question 148591
1.{{{-7x+y=20}}}
2.{{{9x-3y=36}}}
You can multiply eq. 1 by 3 and add the two equations to get an equation only in x.
1.{{{3(-7x+y)=3(20)}}}
1.{{{-21x+3y=60}}}
Add this to eq. 2 to get,
{{{9x-3y-21x+3y=36+60}}}
{{{-12x=96}}}
{{{highlight(x=-8)}}}
Now you can use either eq. 1 or eq. 2 to solve for y.
1.{{{-7x+y=20}}}
{{{-7(-8)+y=20}}}
{{{56+y=20}}}
{{{highlight(y=-36)}}}