What have you mentioned as X here?

this is my attempt check whether this is correct

If V is a vowel, and N is a non-vowel, the arrangment should be,

V,N,V,N,V,N,V,N or N,V,N,V,N,V,N,V

so for vowels no of arrangments - 4!

for non-vowels no of arrangments - 4!

total no. of arrangments = (4!.4!)2