What social problems needed to be addressed in the united states in the late 19th and early 20th centuries

In ohio in 1872, the cleveland massacre was a violent labor dispute at standard oil refineries in cleveland. a takeover by standard oil of the refineries in cleveland. an attempt to stop standard oil from becoming a monopoly. a failed attempt by standard oil to take over other refineries.

The quote below is an excerpt from the charter of the united nations: "the purposes of the united nations are: to maintain international peace and security, and to that end: to take effective collective measures for the prevention and removal of threats to the peace, and for the suppression of acts of aggression or other breaches of the peace, and to bring about by peaceful means, and in conformity with the principles of justice and international law, adjustment or settlement of international disputes or situations which might lead to a breach of the peace . " source:this section implies that the united nations is prepared to do what to keep world peace?

31/3: which equation has the solutions x =?