How successful might he be if he takes the steps you have included...

How successful might he be if he takes the steps you have included in your response? 

Thomas, who is 17 years old, wanted to spend a vacation in Hawaii before his senior year in high school, so he signed a contract to buy a round trip ticket from Austin, promising to pay the full price plus interest upon graduating from high school the following year.  He used the ticket and enjoyed his trip immensely.  Shortly after his return to Austin he decided he did not want to pay for the ticket after all.  He comes to your office to find out what he should do to retract his agreement to the contract and how long would he have in which to do so.