The second number in the given number-pairs is obtained by performing certain mathematical operation(s) on the first number. The same operation(s) are followed in all the number-pairs EXCEPT one. Find that odd number-pair.

25 : 4

The logic followed here Is :

option 1       100 : 7

                  10² = 100

                  10 - 3 = 7

option 2       25 : 4

                  5² = 25

                  5 - 3 = 2 odd

option 3       169 : 10

                 13² = 169

                 13 - 3 = 10

option 4      64 : 5

                     8² = 64

                      8 - 3 = 5