A pen is used to write with为什么要加个with呢？！

求答案~！

is used to ,used to各是什么意思 ？ 造句it is rude to do,have a great time,get used to,make appointments Linda is writing a litter to her pen pal.(改否定句) tim used to be a dancer, but now she is a bit overweight. I want to have a pen pal -your father is a soldier,isn't he?- no,but he used to be. 这里为什么不能回答no, but he used to.? This is a pencil and a pen还是This are a pencil and a pen, There is a pen and a pencil 还是There are a pen and a pencil it is a pen ,isn't it ? ____ ,it is pen he used to be a doctor,_________?