Question 1085489
1.{{{3x-y=1}}}
2.{{{x+2y=12}}}
From 2,
{{{x=-2y+12}}}
So,
{{{3x=-6y+36}}}
Substituting into 1,
{{{-6y+36-y=1}}}
{{{-7y=-35}}}
{{{y=5}}}
Now use either equation to solve for x.
Use the same method for the other two systems of equations.