How many strings are there of four lowercase letters that have the letter x in there?

Answer 1

At least one x?

That would be 26^4 - 25^4, namely the total number of strings minus the number of strings that DON'T include x.

The first part of that is the number of four-letter strings chosen from a 26-letter alphabet, and the second part is the number of four-letter strings chosen from a 25-letter alphabet (i.e., one without x in it).

Answer 2

Millions of them. Details: x can be in position 1 followed by any other letter in the last 3 places. similarly x can be in positions 2,3,4 with other letters in other places. And in last case, x can be in all four places. That is 26C3 + 26C3 + 26C3 + 26C3 + 1. That would be a huge number. Read ur qstn again - u never mentioned meaningful words or even words - u just said strings of four lowercase letters that have 'x' in them. Assumption: Strings mean alphabets only.