The average age of 29 students in a class is 26 years. If the age of the teacher is also included, the average age of the class becomes 26.4 years. Find the age of the teacher?

38 years

Total age of 29 students = 29 × 26 = 754 years

Total age of 29 students + 1 teacher = 30 × 26.4 = 792 years

Age of teacher = 792 - 754 = 38 years