How does democracy ensure the well-being of the people?

The needs of the few out weight the needs of the many but this can be problematic because the "many" don't have necessary intelligence over diplomatic strategies, economics, politics, military etc and the majority can cause problems to a society in case they become "greedy" or dependent on the system. In fact, it is more likely that democracy is an idea in the sense that people think it's real when in reality there are a board of leaders in place making the decisions. It is also know that they aren't meant to last.
you should get both sides, that's what it means to be educated so why does your school ask you to get only one side...
it doesn't necessarily ensure the well-being in society, it isn't "all good" or even existent in most cases only believed to be in place.
even the school has an agenda, thank your teacher for not enlightening your class.

In 911, a group of vikings lead by rollo besieged paris and chartres. after a victory near chartres on 26 august, charles decided to negotiate with rollo. the talks were led by hervé, the archbishop of reims. this resulted in the treaty of saint-clair-sur-epte, which granted rollo and his soldiers all the land between the river epte and the sea. it also granted him brittany, "for his livelihood". at the time, brittany was an independent land which france had not been able to conquer. in exchange, rollo promised the king his loyalty and military assistance when needed. also rollo also agreed to be baptised and to marry gisela, the king's daughter. the territory given rollo is about the same as upper normandy. this would grow to become normandy under rollo's descendants. - wikepedia