They are two equation you can't add them together or factories them together .
You should do it one By one ,
• For 2x+3y=20
Move 3y behind so that you can form
2x=20-3y
• For -2x+y=4
Move -2x behind as you have already figure it above , so it should be
Y=4+2x
Than you eliminate it into your questions :)
Hope this helps !!