A new term has begun. Teachers are 1 about the fact that new students are not easy to deal with. They like to bring cell phones and MP3 players to school. What is worse , some students even use cell phones 2 out-of-class matters in class, or sometimes just for fun. Some 3 students listen to MP3 players when they are having a lesson that they are not interested in.
Are these new students really that 4? “Yes.” Says Delaney Kirk, a professor（教授） at Drake University. But she adds it’s not their fault.5, the teachers should be blamed(责备). Mrs Kirk first began thinking about students’ manners six years ago. “I had my first class in which students were sleeping or talking to each other. It seemed that learning well had nothing to do with them.” She says. “At first, I got worried about this.” But then I said to 6 , “You’re giving lessons, and you need to manage this kind of situation. These students need to know more about manners. It’s time to help them develop some good 7. They shouldn’t waste time doing nothing when they are young. Sooner or later, they may regret(后悔) the time they 8.”
Mrs Kirk also makes a list of suggestions to help teachers better manage（驾驭） their classes. The following are among her suggestions:
On the first day of class, tell students how they will benefit(受益)by taking the class and the importance 9 listening carefully in class.
Do not allow them to bring cellphones or MP3 players to the class at all.
Tell them10 to use cell phones or MP3 players properly(适当地).

已知方程组 $\{\begin{array}{c}x+2y=k\\ 2x+y=1\end{array}$ 的解满足x+y=3，求k的值．

读世界不同尺度的区域轮廓图，完成下列各题。

小芳同学用如图所示的实验装置探究“水沸腾时温度变化的特点”．

如果a﹣3与a+1互为相反数，那么a=____