So it turns out that he could have picked anything to explain this, and hopefully done out the calculation, and we'll do this ourselves.

结果是他可能用任何事情,来解释这个说法，有希望完成这个计算，而且我们将自己做这件事。

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but if you explain it to your friend that you or she should not have or should have done something,

如果你想要向你的朋友解释，或者她应该做某事的时候，

I should have 课堂 - SpeakingMax英语口语达人

Use this pattern in any situation where you want to explain you've done it before.

当你想解释之前已经做过某事的时候，可以在各种情形下使用这个句型。

I've already 课堂 - SpeakingMax英语口语达人