4x+y= x
Move all x term to left side
4x-x+y=0
Subtract 4x from 3x
3x+y=0
Move y term to right side
3x= -y
Divide both sides by 3
X= -y/3
Ok so if it's
4x+y= z solve for x
Move y to right side
4x= -y +z
Now divide both by 4 to get x alone
X= -y/4 + z/4