Two of the strings 和 Two strings 都可以,要看句子和上下文.
例句：
Two strings in the violin are broken
Two of the strings in the violin are broken
两句的意思看似一样,但第二句意味着小提琴有多过两条弦,而第一句则没有这个意思（虽然我们大家都知道小提琴有四条弦）.