A. 28 (4 / 7) years
B. 31 (5 / 7) years
C. 32 (1 / 7) years
D. 35 (5 / 7) years
=> Grand Parents -> number = 2, Average age = 67
=> Parents -> number = 2, Average age = 35
=> Grandchildren -> number = 3, Average age = 6
=> Average Age of Family = ( 2 x 67 + 2 x 35 + 3 x 6 ) / ( 2 + 2 + 3 )
=> Average Age of Family = ( 134 + 70 + 18 ) / 7 = 31 (5 / 7) years