The average age of three boys is 20 years and their ages are in proportion 3:5:7. What is the age in years of the eldest boy?	Choose the correct choice from the following.
A) 6
B) 9
C) 28
D) 24
E) 21
3x + 5x + 7x = 60   x =4   7x = 28   Answer:28
<result>C</result>
The average age of three boys is 20 years and their ages are in proportion 3:5:7. What is the age in years of the eldest boy?