teacher gone missing

.my high school math teacher disappeared when i was six teen,but now i have a reason to believe shes not dead. a week ago before my family reunion, i received a mysterious letter that appears to be in code.kinda like the puzzles she once gave her students . now, at the reunion discover that several i discover that several of my classmates have received similar letters.its telling us shes a the pecific ocean on an island .... what do i do now !