 
 <translate> Another way: Any letter (x, y, z, w) can be included or not. So, we have 2^4 combinations - 4 empty combination = 12 combinations
The final answer: (B). <hau> Wata hanya: Duk wani harafi (x, y, z, w) za a iya haɗa shi ko a'a. Saboda haka, muna da 2^4 hade - 4 m hade = 12 hade Amsar ƙarshe: (B). 