Answer:
Equation in terms of k about the average age is:
(2k + 61) / 5 = 17
After solving the equation, k = 12 years
Explanation:
Age of Roxanne = k years
Age of the sister = (k + 8) years
Age of brothers = 21, 18 and 14 years
Total number of siblings = 5
Average age of siblings = [k + (k + 8) + 21 + 18 + 14] / 5
or, 17 = [2k + 61] / 5
or, 85 = 2k + 61
or, 24 = 2k
or, 12 = k
So, k = 12 years