x-y=4
-4+2y=-4 Start with the second equation by adding 4 to both side of the equation. that will give you 4-4+2y=-4+4. the answer is 2y=0. Now if you divide both sides by 2 you end with 2y/2=0/2, the result is y=0.
Now substitute this answer for y in the first equation of x-y=0. Once you substitute it should look like this, x-0=4, therefore, x=4.
Hope this helps you.
