The youngest of 4 children has siblings who are 1, 4, and 7 years older than she is. If the average (arithmetic mean) age of the 4 siblings is 17, what is the age of the youngest sibling?  Choose the correct choice:
A) 10
B) 11
C) 12
D) 13
E) 14
x + (x+1) + (x+4) + (x+8) = 68   4x + 12 = 68   4x = 56   x = 14   The answer is 14.
<result>E</result>
The youngest of 4 children has siblings who are 1, 4, and 7 years older than she is. If the average (arithmetic mean) age of the 4 siblings is 17, what is the age of the youngest sibling?