We don't write letters in English.
Letters aren't written in English by us.
Letters aren't written by us in English.
We heard her singing a beautiful song yesterday.
A beautiful song was heard to sing by us yesterday.
A beautiful song singsing by her was heard by us yesterday.
We heard her singing a beautiful song yesterday.
A beautiful song was heard to sing by us yesterday.（这句不对，SHE WAS HEARD SINGING A BEAUTIFUL SONG BY US YESTER DAY ）
A beautiful song singsing by her was heard by us yesterday.（A BEAUTIFUL SONG SUNG BY HER WAS HEARD YESTERDAY ，但这样，这意思和原句有点出入，）
A BEAUTIFUL SONG WAS HEARD BY US BEING SUNG BY HER YESTERDAY ，这样意思没变，但还是建议第一种，以SHE作主语
We don't write letters in English 中don't 改成are't 这东东不能用助动词
Letters aren't written in English by us 都以是Letters做主语 了第三人称 用 does 所以为does't
下一题也是如此
下面全对 OK