If Janice was 22 years old z years ago and Lisa will be 20 years old in p years, what was the average (arithmetic mean) of their ages 7 years ago?	Select the correct option.
A) (z + p)/2 B) (z - p + 28)/4 C) (z - p + 18)/4 D) (z + p + 38)/2 E) (z - p + 28)/2
Today, J = z+22 and L = 20-p   7 years ago, J = z+15 and L = 13-p   The average of their ages was (z-p+28) / 2   The answer is (z - p + 28)/2.
<result>E</result>
If Janice was 22 years old z years ago and Lisa will be 20 years old in p years, what was the average (arithmetic mean) of their ages 7 years ago?