The average age of three boys is 15 years and their ages are in proportion 3:5:7. What is the age in years of the youngest boy?	Choose the correct answer:
A) 8
B) 9
C) 7
D) 5
E) 2
3x + 5x + 7x = 45   x =3   3x = 9   Answer: 9
<result>B</result>
The average age of three boys is 15 years and their ages are in proportion 3:5:7. What is the age in years of the youngest boy?