to sub
solve for 1 variable
pick an eas one that isn't tangles up wht frathctions or such
x in second equiaton
2y-x=-7
-x=-7-2y
x=7+2y
sub 7+2y for x
(7+2y)-4y=11
7+2y-4y=11
7-2y=11
minus 7
-2y=4
divide -2
y=-2
sub
x=7+2y
x=7+2(-2)
x=7+-4
x=3
(x,y)
(3,-2)