Đáp án `+` Giải thích các bước giải:

`6.` I prefer listening to classical music now, although when I was young I couldn't stand it.

`to` I didn't use to like classical music

`***` S + didn't + use to + V

`7.` I have just lost interest in my work.

`to` I used to be interested in my work

`***` S + used to + V

`8.` Dennis gave up playing football one year ago.

`to` Dennis used to play football

`***` S + used to + V

`9.` There were many tree-lined streets in my hometown but now there is none of them.

`to` There used to be many tree-lined streets in my hometown

`***` There + used to be + N

`10.` Children didn't play with high-tech devices at an early age but now they do.

`to` Children didn't use to play with high-tech devices at an early age

`***` S + didn't + use to + V