Answer: 676
Step-by-step explanation:
The total number of letters in English alphabet {From A to Z} = 26
We assume that the repetition of letters is allowed.
If we fix H at the first position , then the number of ways to make three-letter strings that begin with H is given by :-
[tex]1\times26\times26=676[/tex]
Hence, the number of ways to make three-letter strings that begin with H is 676.