Answer: There are 676 three-letter strings that begin with J .
Explanation:
The number of letters in English Alphabet = 26
If first letter is fixed as J , then the number of ways to make 3 letters strings [repetition is allowed ] is given by :-
(The first place is occupied by J and the rest of the two place has 26 ways of getting any letter)
Now, there are 676 three-letter strings that begin with J .