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 choice:
A) 7	B) 9	C) 11	D) 13	E) 14
Explanation:   3x + 5x + 7x = 45   x =3   3x = 9   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?