If 'x' is a positive integer, then ...
-- the smallest 'x' could be is ' 1 '
-- the smallest '3x' could be is ' 3 '.
-- the greatest '2y' could be is (13 - 3) = 10
-- the greatest 'y' could be is ' 5 '.
So, ALL of the possible values of (x,y) are:
==> x=1, y=5
==> x=3, y=2
And that's all. There are no other possibilities.
