In this case I don't know where to start.

A shop has 42 different posters, in various quantities, lying flat in a
storeroom on level 2.

Each day someone rolls some of these posters and puts them in mailing tubes.

The rolled posters in the tubes are then taken downstairs to the shop.

So that I don't run out of posters I need to keep track of how many are
lying flat on level 2, how many I rolled today and how many are on the shop
floor.

I'm really stuck so any help at all will be most appreciated indeed.

Thanks,

Tagger.