What are the problems in Tuck Everlasting?
I think that your question is referring to the types of conflict that are present in Tuck Everlasting.
Man vs. man is present in the novel. The man in the yellow suit wants to know about the Tuck family and gain knowledge of the spring. Once he has possession of the spring, he plans to basically bottle and sell the water to the highest bidder. This of course is directly against what the Tuck family believes should be done with the spring. The man in the yellow suit tries to use Winnie as leverage against her parents and against the Tucks, but Mae does not let that happen. She hits the man in the yellow suit in the head with the butt of a shotgun, and he dies soon after.
His death introduces a new type of conflict. The conflict is man vs. society. The constable witnessed Mae striking the stranger, and he put her in jail to await trial and punishment. The Tuck family knows that Mae did wrong and should be held accountable by the law. Of course if that were to happen, their secret would be out. The Tuck family opts for a prison break.
Which brings me to the final type of conflict -- man vs self. Winnie struggles with her own emotions and decisions regarding two specific events. She has an internal conflict with whether or not she should drink the spring water and become an immortal or not. In the end, she chooses to pour the bottle over the toad. Her other internal conflict is over whether or not she should help break Mae out of jail. She wants to help the Tucks, but she knows that she could get into huge trouble. Winnie does choose to help break Mae out and suffer the consequences.