you bet
You can be sure; absolutely; definitely. A: "Hey Frank, do you want to come with us to the movies?" B: "You bet I do!" A: "Is it OK if Frank brings his girlfriend?" B: "You bet! Tommy's bringing Sarah as well, so it's no problem at all."
You bet!
1. Inf. Yes. Tom: Are you coming to the party? Jane: You bet! Charlie: May I borrow your hammer? Mary: You bet!
2. Inf. You're welcome. Tom: Thank you. Jane: You bet. Sally: I appreciate it. Mary: You bet.