(I'll) tell you what

A phrase indicating that the speaker is going to present a suggestion or their opinion on something.

表示说话人将对某事提出建议或意见的短语。

我的主张(或意见、建议)是…;你听我说

I'll tell you what - we'll split the money between us.

听我说——我们两人把钱分了吧。

Tell you what, why don't you go out for a run and I'll watch the kids for a while.

这样吧，你出去跑会儿步我来照看孩子们。