28人买可乐喝，3个可乐瓶盖可以换一瓶可乐，那么要买多少瓶可乐，够28人喝？假如是50人，又需要买多少瓶可乐？-28 people buy cola drink, 3 for a bottle of Coke Coke bottle can then buy many bottles of Coke, 28 people to drink enough? If it is 50 people, how much they need to buy a bottle of Coke?