Answer:
84
Step-by-step explanation
Case 1: Five A's and One B
Total number of letters = 6
Total number of words possible = 6
Case 2: Five A's and Two B's
Total number of letters = 7
Total number of words possible = 21
Case 3: Five A's and Three B's
Total number of letters = 8
Total number of words possible = 56
Case 4: Five A's and no B's
Total number of letters = 5
Total number of words possible = 1
Total number of possible words will be the sum of all three cases.
Therefore, the total number of words that can be written using exactly five A's and no more than three B's (and no other letters) are 1+6 + 21 + 56 = 84