Clue two is arbitrary to the puzzle as the number is not given. That the salesman asked for 3 clues does not cancel the belief that the woman thought one clue sufficient to begin with. Assuming twins in the population are a rarity and most families have a small spread of years between siblings, I would guess the answer at 1 4 9. This would be the greatest spread that allows clue 3 to make sense when the liklihood of piano lessons being more common for nine year olds than 6 year olds.