Average age of 20 student is 21 years. 2 students leave the group and 1 new student joins the group. The average now becomes 20 years. If age of one of the student who left the group is 26 years and the one who joined is 20 years, then what is the age (in years) of other student who left the group?

Answer: Option B

Average age of 20 students = 21 years
Total age of 20 students = 21 × 20 = 420
2 students leave and one student come in group.
Total age of 19 students = 19 × 20 = 380 years
Student left
420 - A - B + N = 380
26 + B - 20 = 40
B = 40 - 6 = 34 years