How do Percy, Annabeth, and Grover survive the challenge they face in this chapter?

Percy, Annabeth, and Grover try to take a bus to start their quest. While they are on the bus Percy's old math teacher Mrs. Dodds  who is actually a fury shows up disguised as an old lady along with the other two furies. Annabeth puts on her enchanted Yankees hat, given to her by her mother, which turns her invisible. Grover takes their backpack and Percy takes his pen/sword. The plan was for Percy to sneak off the bus with Annabeth's hat but instead of doing that Percy starts killing the furries with riptide (his sword) and ends up destroying the bus and all of their money and supplies. Then Annabeth, Grover, and Percy head out on their own to get to their destination.