To find the outlet that sold the greatest amount of copies of album X in July and August, we need to add the number of copies sold in each outlet for those two months.
Outlet A: 80 + 90 = 170
Outlet B: 60 + 70 = 130
Outlet C: 70 + 80 = 150
Outlet D: 90 + 80 = 170
Outlets A and D both sold the greatest amount of copies of album X in July and August, with 170 copies sold each. Therefore, the answer is either A or D.