The mass of the glass is 25.2 g. The mass of the glass with water is 107.2 g. Find the mass of water.

The mass of water in a glass will be equal to the difference between the masses of water together with the glass and the mass of the glass itself.
m = m1 – m2, where m1 is the mass of the glass with water (m1 = 107.2 g), m2 is the mass of the glass (m2 = 25.2 g).
Let’s calculate the mass of water:
m = m1 – m2 = 107.2 – 25.2 = 82 g.
Answer: The mass of water in a glass is 82 g.