Four number-pairs have been given, out of which three are alike in some manner and one is different. Select the number-pair that is different. (Any operation on digits is not allowed)

197 : 66

THE LOGIC;

(the 2nd number x 3 + 5 = 1st number)

So,

1) 326 : 107

326 : 107 → 3 x 107 + 5 = 321 + 5 = 326

2) 239 : 78

239 : 78 → 3 x 78 + 5 = 234 + 5 = 239

3) 308 : 101

308 : 101 → 3 x 101 + 5 = 303 + 5 = 308

4) 197 : 66

197 : 66 → 3 x 66 + 5 = 198 + 5 = 203 is not equal to 197.

Thus, 197 : 66 is correct.