No specific question has been given.
Probability of Bob throwing the first six is 1/6=16.67%
Probability of Chuck doing so is 5/6*1/6=5/36=13.89%
Probability that Dan throws the first six is 5/6*5/6*1/6=25/216=11.57%
Probability that none throws a six is 57.87%
16.67+13.89+11.57+57.87=100%