一、二班共有100名学生参加期末体育测试，两班的平均达标率为81%，其中一班的达标率为87.5%，二班的达标率为75%，设一班有学生x名，二班有学生y名，根据题意，可以得到方程组____．

（2015•东营）东营市出租车的收费标准是：起步价8元（即行驶距离不超过3千米都需付8元车费），超过3千米以后，每增加1千米，加收1.5元（不足1千米按1千米计）．某人从甲地到乙地经过的路程是x千米，出租车费为15.5元，那么x的最大值是（　　）

阅读下文，回答相关问题。
       【甲】吴广素爱人，士卒多为用者，将尉醉，广故数言欲亡，愤恚尉，令辱之，以激怒其众。尉果笞广。尉剑挺，广起夺而杀尉，陈胜佐之，并杀两尉。召令徒属曰：“公等遇雨，皆已失期，失期当斩。籍弟令毋斩，而戍死者固十六七。且壮士不死即已，死即举大名耳。王侯将相宁有种乎！”徒属皆曰：“敬受命。”乃诈称公子扶苏，项燕，从民欲也。袒右，称大楚。为坛而盟，祭以尉首。陈胜自立为将军，吴广为都尉，攻大泽乡，收而攻蕲。乃令符离人葛婴将兵徇蕲以东攻铚、酂、苦、柘、谯，皆下之, 行收兵。比至陈，车六七百乘，骑千余，卒数万人。
                                                                                                                                                                                                                            （节选自《陈涉世家》）
        【乙】秦二世元年七月，陈胜等起大泽中。其九月，会稽守^①通谓梁^②曰：“江西皆反，此亦天亡秦之时也。吾闻先即制人，后则为人所制。吾欲发兵，使公及桓楚将”。是时桓楚亡在泽中。梁曰：“桓楚亡，人莫知其处，独籍^③知之耳。”梁乃出，诫籍持剑居外待。梁复入，与守坐，曰：“请如籍，使受命召桓楚。”守曰：“诺。”须臾，梁睨^④籍曰：“可行矣！”于是籍遂拔剑斩守头。项梁持守头，佩其印授。门下大惊，扰乱，籍所击杀数十百人。一府中皆慑伏，莫敢起。……于是梁为会稽守，籍为裨将，徇下县。
                                                                                                                                                                                                                  （节选自《史记·项羽本纪》）
        【注释】①会稽守：会稽郡的郡守。②梁：项梁，是项羽的叔父。③籍：项籍。项籍字羽，所以又称项羽。④睨：斜眼看。

    Jia Zuosheng, 27, used to work as a security guard (保安) at the library of Tsinghua University. But a few months ago, he became a college student in Lishan College in Shandong and he studies math there now. When hearing this news, many people were surprised. On school opening day, many reporters waited outside the school gate to interview him.

    “I was born in a poor village in Shandong Province," said Jia. "Our village has never had a college student. Most boys work in town after growing up. I failed the National College Entrance Exam（高考）twice. Then I went to Beijing to find jobs. In the following years, I went on studying by myself while working.”

    At the end of 2009, Jia found a job as a security guard at the library of Tsinghua University.“I cherished (珍惜) the job very much because it gave me a good chance to read books," Jia said.“I usually worked at night so I had plenty of time to study in the daytime.” When he had problems that he couldn't work out, Jia asked the students at Tsinghua for help. "My dream is to be a college teacher. So I need further education. That's the reason why I took the National College Entrance Exam again," Jia said. “I wish to educate students with my knowledge and love and help them enjoy true, kind and beautiful things.”

    Jia's mother said Jia has always been independent（独立的）and knows what he wants. But she has other worries. "It's difficult to find such a good job at present as a library guard in Tsinghua University. I'm not sure if this is a right decision.” “I will never regret(后悔），”said Jia. "Everyone will have a new start. It's the end, and the beginning.”