Your question is Expected Value for Biased Coin. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Explain how you would compute the expected payout for a game where a biased coin determines win or loss, with a reward of $10 for win and $0 for loss, and a $1 fee to play.