If the total amount of sand that Jed put in his sandbox was 85.5 lbs, and he put 5 bags of sand in his sandbox, then all we need to do to find the amount that each bag weighed is to divide the total weight by the amount of bags he put in.
85.5 / 5 = 17.1
Each bag weighed 17.1 lbs.
Hope that helped! =)