Question 504466
Assume x be the Age of the student.
Average age of 40 students = 12 years
Total age is :
  40x = 12*40
40x = 480  -> Equation 1

Let teachers age be y
Average age of 41 people (40 studenets + 1 teacher) = 13 years
Hence total age 
   40x + y = 533  -> Equation 2 

Subtracting equation 1 from equation 2, we get
 y = 53

Age of teacher  = 53 years