In this passage, the implication in the text is that the country has called every generation of Americans to prove their national loyalty. The word that most closely resembles the meaning of "summoned" is "requested." When we do not know the meaning of a word and we do not have a dictionary at hand, we can try to determine the meaning through the context provided in the rest of the sentence.
Answer: Your roomate and you would normally pay the same amount as the other. So the rent would be divided evenly. Although, sometimes it can be split more than evenly if one person is willing to pay for more.
