不管三七二十一。(Bùguǎn sān qī èr shí yī.)Regardless of the consequence.

Explanation

“三七二十一”原来是一句乘法口诀，意思是3个七等于21。后来常用这句话表示不顾一切，不管结果怎样，一定要做某件事。
“三七二十一” is a multiplication table. It means three times seven is twenty-one. This sentence means regardless of the consequence to show one’s determination to do something.
Words:

酒jiǔ:wine;

拒绝jùjué:refuse.

Sentences

1、Jiǎ: Lǐ Míng bú zài ma?
甲：李明不在吗？

A: Isn’t Li Ming here?
Yǐ: Tā jiē le gè diànhuà, ránhòu bùguǎn sān qī èr shí yī jiù pǎo chūqu le.
乙：他接了个电话，然后不管三七二十一就跑出去了。

B: He just ran out regardless of everything after answering a phone.
2、Jiǎ: Tā bùguǎn sān qī èr shí yī jiù hē xià le nà bēi jiǔ.
甲：他不管三七二十一就喝下了那杯酒。

A: Regardless of the consequence, he drank that glass of wine.
Yǐ: Wǒ yuán yǐwéi tā huì jùjué de.
乙：我原以为他会拒绝的。

B: I thought he would refuse.