You’re on

We use this expression to accept an offer or a challenge.

You can use this phrase in ………… language.

 Spoken
 Written
 Informal

Example 1
A: If you help me with this report, I’ll buy you a drink afterwards.
B: You’re on.

Example 2
A: I bet you can’t eat all this food in 20 minutes.
B: You’re on. It’s easy.