I'll tell you what
US /aɪl tɛl ju wʌt/
UK /aɪl tɛl ju wʌt/

1.
あのね, いいかい
used to introduce a suggestion or a solution to a problem
:
•
I'll tell you what, let's just order pizza tonight.
あのね、今夜はピザを注文しよう。
•
You're struggling with that? I'll tell you what, I can help you.
それに苦労しているのか?あのね、私が手伝ってあげられるよ。