I'll tell you what. 让我告诉你吧
当你有非常确切、果决的意见或想法想要传达给对方时-可以说“I'll tell you what.”这也是“I'II tell you what l will do.”或者“I'll tell you what might be a good idea.”的省略形式，在口语上自然更常使用。
模拟对话
给忠告
Lisa: How was your presentation?
莉莎：你的报告做得怎么样？
Jim: Pretty good. How about yours?
吉姆：还不错。你呢？
Lisa: Bad.I didn't prepare for it at all last night.
莉莎：很不好。我昨晚一点都没准备。
Jim: I'll tell you what.stop talking to Jason all night long and you'll find you have more time to prepare for your studies.
吉姆：计我麓诉簿吧，你如果不要整晚都跟杰森讲电话，你一定会有更多的时间可以准备功课。
在这段对话当中，Lisa告诉Jim她没为报告做准备，而Jim其实知道为什么，于是直接以“l'II tell you what”对她提出建议与忠告。