Answer:
The answer would be -8R.
I think that is the answer solved...sorry.
If we do it algebraically, we get
x + y = 420
This is the simplest equation. You see now this is a linear pair in two variables. Thus, there will be infinitely many solutions.
E.g - 419 + 1 = 420
42 * 10 = 420
21 * 20 = 420
etc,....
Where is it? I can’t help you without it.