Average age of 7 girls is 12. When age of a boy is included the average becomes 13 years. Find the age of boy.A15B18C16D20Answer: D. 20 Read Explanation: 20 Total age of 7 girls = 84 Total age of 8 students when boys is included = 13 x 8 = 104. Age of boys = 104 - 84 = 20Read more in App