QIOK : MMKO :: YAWC :?

26 = (2 x 15 - 4)

? = 15

As, 235 ? 25³

The middle digit of first term becomes power to the next term.

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.