CONCEPT: The question tests the basics of alligation 

SOLUTION :

 
Spirit in 1 litre mix of X= 5/7 lit

Spirit in 1 litre mix of Y= 7/13 lit

Spirit in 1 litre mix ofZ= 8/13 lit

Using Alligation:

A : B

5/7 7/13


8/13


1/13 : 9/91

 = 7 : 9 (OPTION D)