2w-y=7w-z; solve for w
2w-y=7w-z2w-y-7w=-z2w-7w=-z+y-5w=-z+y5w=z-yw=1/5z-1/5y done.
2w-7w=y-z-5w=y-z divide both sides by -5w=y-z\-5w=y-z divided by -5
