My singing voice isnt that good.

我的嗓音不怎么好。

Your sister is engaged, isnt she?

你的姐妹已经订婚了，是吗？

Its a great party, isnt it?

这个派对很不错，是吗？

Is she thin? No, she isnt.

她瘦吗？不，她不瘦。

What you said, I think, isnt true.

我认为你说的话是不真实的。