How do you add intergers with different signs

Which of the following factors would be a likely reason for low population density

The 14th amendment overruled the supreme court case of dred scott vs. sandford. the landmark supreme court case determined which of the following points? a.slaves could not be citizens b.non-landowners could not be citizens c.blacks could not be citizens d.all persons born or naturalized in the united states vary differently in citizen status.

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?