First to get X you have to do 3x=5x-64. Which makes X equal to 32. Then to get Y you do 32+y=180 since y + x would be a straight line and a straight line is 180 degrees. That makes y equal to 148. A theorem you use to find x is vertical angles theorem which states that vertical angles are the same so that is why you can put 3x=5x-64 to find x. And then you use that same theorem to know that the angle right next to the 3x or (5x-64) is equal to why so that is why you can do 32+y=180.
I hope this helps :)