Final answer:
The pre-Algebra teacher named Mrs. Dodds is vaporized by Percy Jackson in Rick Riordan's book, 'The Lightning Thief', which marks the start of his adventures.
Step-by-step explanation:
The pre-Algebra teacher who Percy vaporizes is Mrs. Dodds. In the book The Lightning Thief, which is the first book of the Percy Jackson & the Olympians series by Rick Riordan, Percy is baffled when the Fury disguised as Mrs. Dodds, a seemingly normal teacher at Yancy Academy, turns into a creature and attacks him during a school field trip. The vaporization is an unexpected event that symbolizes the beginning of Percy's journey into the world of Greek mythology and his own discovery as a demigod.