The sum of -18 and 39 is 21.
89
By the uniqueness of integers, the only integer for 39 is 39 itself. And that cannot have a sum of 3.
It is: 1225+39 = 1264
The 3rd magic sum in the 39 clues game is 42.
The answer is 39.
18
It is: 127+39+262 = 428
41
123
66
They are 16+23 = 39