Hello DrdumbomYou're right so far. Let me continue:

With A + B + B there will be two other letters chosen from the remaining 3. So we have two processes:

- Choose 2 out of 3 remaining letters. This can be done in ways.

- Arrange the 5 letters, which include a repeated B. This can be done in ways.

So A + B + B can be done in ways.

Similarly A + A + B can be done in ways.

And then in a similar way A + A + B + B + one other letter can be chosen and arranged in ways.

Therefore the total no of 'words' .

Grandad