Play by the rule. I'll do

In this morning's NPR's diane reim show, I learned two phrases

1. "play by the rule"
e.g. "they're the second or third generation of latino immigrant and they always play by the rule."
You can also add another phrase - pay tax on time.
I used to use abide by the law, which sounds too formal :)

2. "I'll do"
When asked by the host which panelist will say something, one of the panelist says "I'll do", meaning 让我来 or 我来说好了。