|A) decrease||B) stay the same|
|C) increase four fold||D) increase to more than double|
The best approach is to pick a number that satisfies the rules that x and y are greater than 0. So for example you could choose 25 for y.
The value of x before doubling is then 25 - 50/25 = 23
The value after doubling y will be 50 - 50/50 = 49, which is more than double.