What does Miss Adelaide's fiance challenge the gambler to do in Havana?
Gambler Nathan Detroit seeks to organize an unlicensed crap game, but the police, led by Lieutenant Brannigan, are "putting on the heat". All the places where Nathan usually holds his games refuse him entry due to Brannigan's intimidating pressure. The Biltmore garage is the only venue where Nathan can hold the game, but its owner requires a $1,000 security deposit, which Nathan doesn't have. Adding to his problems, Nathan's fiancée, Miss Adelaide, a nightclub singer, wants to bring an end to their 14-year engagement and actually tie the knot. She also wants him to go straight, but organizing illegal gambling is the only thing he's good at. 
Then Nathan spots an old acquaintance, Sky Masterson, a gambler willing to bet on virtually anything and for high amounts. To win the $1,000 security deposit, Nathan bets Sky that he can't take a girl of Nathan's choosing to dinner in Havana, Cuba. The bet seems impossible for Sky to win when Nathan nominates Sergeant Sarah Brown, a sister at the Save a Soul Mission, which opposes gambling.
To approach Sarah, Sky pretends that he is a gambler who wants to change. Sky suggests a bargain. He will get a dozen sinners into the Mission for her Thursday night meeting in return for her having dinner with him in Havana. With General Matilda Cartwright threatening to close the Broadway branch for lack of participation, Sarah has little choice left, and agrees to the date.
take a girl of Nathan's choosing to dinner