I hope this helps you
1)
x= -2y
2. (-2y)+4y=0
0=0
2)
x+2x= -3
x=-1
y= -2
3)
7x+2x+2=4
9x=2
x=2/9
y=2/9+1
y=11/9
You plug -x+16 in for y in x+4y=37 to get x after you multiply x+4y=37 by -1.
-x-4(-x+16)=-37
-x+4x-64=-37
3x-64=-37
3x=27
x=9
Then you plug 9 into either equation to get y.
y=-x+16
y=-(9)+16
y=7
x=9 and y=7