Answer:
the distance from the floor below to the top of the bookcase
Step-by-step explanation:
From the question we are given the following
distance from a stage to the floor below = -3
distance from the stage to the top of a bookcase = 3
The distance from the floor below to the top of the bookcase = distance from a stage to the floor below + distance from the stage to the top of a bookcase
The distance from the floor below to the top of the bookcase = -3 + 3
The distance from the floor below to the top of the bookcase = 0
Hence zero represents the distance from the floor below to the top of the bookcase
