The average age of 12 students is 14 years. If the age of the teacher is also included, the average becomes 15 years. What is the age of the teacher?

27 years

Sum of age of 12 students = 12 × 14 = 168 years

After adding age of teacher

Sum of Age of 12 students + 1 teacher = 13 × 15 = 195 years

Age of teacher = 195 - 168 = 27 years