how can I change sentence not using 得?
得(去声) refers to 'must,have to '
回答得大声  回答 is V.  and 大声 is Adj. So you can make other sentences using V+de (得)+Adj become Adj+V ,but,a point need to notice, for another example,教室得打扫 and 打扫教室 ,though it is can be exchange ,but their means are little difference, the first one has another meaning that the classroom is dirty and need to clean. 

In addition, if the sentence is pronoun+得+ V ,in this condition,you can't exchange like before,for example: 我得去游泳 ,we can't say 游泳我.