.
Under the given condition, the answer (the solution) is not unique.
For example, X = 1, Y = 3 gives X^3 + Y^3 = 28.
X = 2, Y = 2 ====> X^3 + Y^3 = 16.
X = 5, Y = -1 ====> X^3 + Y^3 = 124.
To have a unique solution (the unique answer), additional restriction/restrictions should be imposed.