Answer:
the mass of the empty box is 4/3 kg.
Explanation:
The total mass (box plus 4 books and 2 files) is 2 kg
When half of the load is removed (2 books and 2 files) the mass is 1 3/20.
We have the following equation:
2 kg - (x/2)= 1 3/20 kg
Where x is the total mass of the load (4 books and 2 files)
This steps where followed to solve the equation:
2 -x/2 = (20-3)/20
40-10x=17
23=10x
x=2/3 kg
That is the total mass of the load
Hence
2kg -2/3 kg= 4/3 kg, the mass of the box