First you must find the least possible value of y (if you subtract the least amount from x, then x – y is the greatest). In order to find the least possible value of y, you must find the greatest possible value of x. Since both numbers are integers, the greatest possible value of x is 13, making the least possible value of y =1:
(1 + 13 < 15). That would make 13 – 1 =12.