8 : 28 :: 27 : ?

Explanation:-

First number = 8 and the sum of the digits of the second number is 2 + 8 = 10.
Thus the difference of the first number and the sum of the digits of second number is 10 - 8 = 2.
Similarly, the sum of the digits of third number is 2 + 7 = 9.
Hence the sum of digits of fourth number should be 2 more than 9 i.e. 11
Hence, fourth number is 65.