The students in a certain physical education class are on either the football team or the basketball team, are on both these teams, or are not on either team. If 12 students are on the football team, 15 students are on the basketball team, 8 students are on both teams, and 9 students are not on either of these teams, how many students are in the class?

There are not_____students in Class One as in Class Two.

Many students ______ chances to show themselves in class because the class size is too big.

How many students went to the hockey game?（）

How many dry-power extinguishers has your ship exactly been（）.

In plotting a running fix，how many fixed objects are needed to take your lines of position from? （）

--How many students do you teach? ( )
--__________

In 2002, the same number of students participated in the fund-raiser from class C as from class D. If class D contained 120 students in 2002, how many students were there in class C in 2002?

Practice 1　　阅读下面的对话，根据其内容写一篇有关British classes的说明文。　　要求：　　1. 所写短文应与对话相关内容意义相符，涵盖其要点；　　2. 用你自己的语言表达，可改写对话中的句子，但不可照抄原句。　　注意：　　1. 词数80词左右，开头已为你写好；　　2. 请将短文直接写在答题卡上。　　Marry: Hi, Jack, I heard that you were studying law in Britain. Can you tell me how the classes are arranged there?　　Jack: Sure. Basically, our classes are made up of two major parts: lectures and seminars（讲座）. The lectures are just like the general classes in China.　　Marry: You mean, teachers give presentations, and students listen?　　Jack: Yeah. But the students are free to ask questions. The classroom atmosphere is warmer too.　　Marry: Ok. How about the seminars?　　Jack: In the seminars, students are encouraged to do some case study. In the case study, students are encouraged to share their views with the classmates. Students need to make full preparation. They need not only to study relevant laws, but also to read relevant cases to benefit the class.　　Marry: But what do professors do in the seminar?　　Jack: Professors are only organizers of it. They don’t express their ideas.　　Marry: Does everyone have a chance to express his idea in the seminar?　　Jack: Yes, since our class is very small. Generally, there are only 8 to 10 students in one class.　　Marry: Oh, that is a very small class. How about the lecture? How many students are there in one class?　　Jack: The lecture class is much bigger. Sometimes, there can be more than one hundred of us in one class.　　Marry: I see.　　British classes are made up of two major parts.

How many students（）in your class?

How many students do you teach?（）

In a class of 160 seniors, the ratio of boys to girls is 3 to 5. In the junior class, the ratio of boys to girls is 3 to 2. When the two classes are combined, the ratio of boys to girls is 1 to 1. How many students are in the junior class?