他觉得这样做不对。

Tā juéde zhèyàng zuò bú duì.

He thinks doing this is not right.

如果不对，请告诉我。

Rúguǒ bú duì, qǐng gàosu wǒ.

If it is not correct, please tell me.

这个答案不对。

Zhège dá'àn bú duì.

This answer is not correct.