Okay, if x-y=11, then y + 11 = x
Now, apply this to the next equation. Since we know y + 11 = x, we can use this instead of x
2(11+y)+y=19
22+2y+y=19
22+3y=19
now make 3y alone
3y=19-22
3y=(-3)
y=-1
Plug y to our first equation to get x
x = 11+-1
x=10
Hope this helps :)