Correct Answer: D
Explanation:
Here reverse positions are to be considered.
35-34 = 1. A has position 1.
But when reversed Z has position 1.
42-36 = 6 ; 6 means 1+5
U has position 6 in reverse
55-44 = 11 ; 11 means 6+5
P has position 11 in reverse
64-48 = 16 ; 16 means 11+5
K has position 16 in reverse
Next difference has to be 16+5 = 21
21 is the position of F in reverse
Answer is option d where 73-52 = 21