Respuesta :
Answer:
27
Step-by-step explanation:
Make a tree-diagram for all three-letter code words starting with A. Each path from the top to the bottom contains 3 letters, which is one of the code words beginning with A. There are 9 such code words. Clearly, there are 9 code words starting with B and 9 starting with C. In all, there are 27 code words.
