Question 147753
1.{{{x+y/3=-6}}} 
2.{{{x/5+y/4=-7/4}}}
or in matrix form,
{{{(
 matrix( 2, 2, 
   1, 1/3, 
   1/5, 1/4))*(matrix(2,1,x,y))=(matrix(2,1,-6,-7/4))}}}
Multiply eq. 1 by (-1/5) and add to eq. 2, to remove x.
{{{(-1/5)x-y/15=6/5}}}
{{{x/5+y/4=-7/4}}}
2'.{{{(-1/15+1/4)y=6/5-7/4}}}
2'.{{{(11/60)y=-11/20}}}
Now your two equations, in echelon form, are
1.{{{x+y/3=-6}}} 
2'.{{{0x+(11/60)y=-11/20}}}
or in matrix form,
{{{(
 matrix( 2, 2, 
   1, 1/3, 
   0, 11/60))*(matrix(2,1,x,y))=(matrix(2,1,-6,-11/20))}}}

You can solve for y from 2'.
2'.{{{(11/60)y=-11/20}}}
{{{y=-(11/20)(60/11)}}}
{{{y=-3}}}
From 1,
1.{{{x+y/3=-6}}}
{{{x=-6+3/3}}}
{{{x=-6+1}}}
{{{x=-5}}}