Answer:
I would interpret the statement by using a formula.
Step-by-step explanation:
In order to be scientifical in a research, the scientific method must be used, this means that in this case, Lavoisier should´ve follow a Hypothesis, Objectives, a Methodlogy, Results and made a Discussion and Conclusion.
To prove that the mass gained by the pipe plus the mass of the collected gas "exactly" equaled the lost mass of water, Lavoisier should´ve used this statement as a formula where it proves with numbers that is correct.
For example:
mg= mass gained by the pipe
mc=mass of the collected gas
ml=lost mass of water
mg+mc=ml