when camping alone , mr adam uses all of the water in 12 days, then when mrs adams and mr adams camp together they use all of the water in storage in 8 days. if mrs adams camps alone in how many days will she use all of the water?

In order to find out how many spools of threads are in the box, take the weight of the box, and divide it by how much each spool weighs:

8 divided by 1/2 < this is your equation. When dividing fractions, you keep the first value (8), switch the operation (so instead of dividing, you are now multiplying) and you flip the second value (1/2 becomes 2/1). Your new equation should be:

8 (or 8/1) x 2/1 which is basically saying 8 x 2, which equals 16. 

There are 16 spools of thread in the box.